LECTURE 1Introduction to Acoustical Design

Matias Remes MSc FISE A acoustics

Rak-433415 Building Physics Design 2

ACOUSTICAL DESIGNAutumn 2015

Course arrangements

Schedule

bull Lectures (6) 89-1310 Tue 1615-20 in hall R2 main themesndash 89 Lecture 1 Introduction basic concepts of acoustics

ndash 159 Lecture 2 Airborne sound insulation

ndash 229 Lecture 3 Impact sound insulation

ndash 299 Lecture 4 Room acoustics

ndash 610 Lecture 5 HVAC noise control vibration isolation

ndash 1310 Lecture 6 Traffic noise guidelines and regulations

bull Exercises (5) 149-1210 Mon 1615-18 in hall R2

bull Design exercise notified later

bull Exam 16122015 (20102015 for students from previousyears)

Execution

bull Compulsory

ndash Design exercise

ndash Exam

bull Recommended and desirable

ndash Attending lectures

ndash Solving exercies independently at home

bull Course books

ndash RIL 243-1-2007 (only available in

Finnish)

ndash Master Handbook of Acoustics

EverestampPohlman (a few sections to be

notified later)

The scope of acoustics

[Lindsay 1964 muutettu]

[Lindsay`s wheel of acoustics

1964 modified Remes]

Brief history of acoustics

rdquoAcoustics is a science of the last thirty yearsrdquo

Physicist Dayton Miller 1931

History

bull 6th century BCPythagoras investigates the relation between the length and pitch of strings

bull 325 BCAristotle writes about the production and reception of sound and echoes

bull 27 ADMarcus Vitruvius Pollio De Architectura first instructions on the acoustic design of theaters

bull 800s Islamic culture produces new knowledge on sound-related phenomena(eg hearing and speech production)

bull 1500sThe effects of Renaissance cathedrals on music

Creek aκουειν = rdquoto hearrdquo

History

bull Mid 1600s

Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings

bull 1670`sFirst purpose-built concert hall is finished in London

bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework

bull 1816

P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)

History

bull Beginning of 1800s

Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms

bull 1850

Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also

bull 1860s

Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance

bull 1876

A G Bell invents the microphone (however condensator microphone is notinvented until 1916)

bull 1877

Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration

History

bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard

Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch

Sabine equation for calculating the reverberation time

bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall

bull 1920Efirst patented acoustical tile

bull 1927First anechoic chamber built (F Watson)

History

bull 1930s

First sound level meter (P Sabine)

bull 1930s

Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities

acoustics becomes a tool for humans to control the environment

bull 1943

The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established

the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s

Acoustics as a field of science and

technologybull Old field of science but significant effects not until the 20th century

bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies

ndash Hearing protection in industrial labour

ndash Privacy in residential buildings

ndash The building of spaces which work according to desired function

bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing

ndash Speech communication

ndash Music

ndash Warning signals

ndash Sound in nature

Acoustical design of buildings

rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan

estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo

Tekniikan lisensiaatti Eero Lampio 1962

The rdquofour-fieldrdquo of acoustical design

Acoustical design of buildings

(Architecturalacoustics)

Roomacoustics

Building acoustics

Noisecontrol

Vibrationisolation

The rdquofour-fieldrdquo of acoustical design

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Schedule

bull Lectures (6) 89-1310 Tue 1615-20 in hall R2 main themesndash 89 Lecture 1 Introduction basic concepts of acoustics

ndash 159 Lecture 2 Airborne sound insulation

ndash 229 Lecture 3 Impact sound insulation

ndash 299 Lecture 4 Room acoustics

ndash 610 Lecture 5 HVAC noise control vibration isolation

ndash 1310 Lecture 6 Traffic noise guidelines and regulations

bull Exercises (5) 149-1210 Mon 1615-18 in hall R2

bull Design exercise notified later

bull Exam 16122015 (20102015 for students from previousyears)

Execution

bull Compulsory

ndash Design exercise

ndash Exam

bull Recommended and desirable

ndash Attending lectures

ndash Solving exercies independently at home

bull Course books

ndash RIL 243-1-2007 (only available in

Finnish)

ndash Master Handbook of Acoustics

EverestampPohlman (a few sections to be

notified later)

The scope of acoustics

[Lindsay 1964 muutettu]

[Lindsay`s wheel of acoustics

1964 modified Remes]

Brief history of acoustics

rdquoAcoustics is a science of the last thirty yearsrdquo

Physicist Dayton Miller 1931

History

bull 6th century BCPythagoras investigates the relation between the length and pitch of strings

bull 325 BCAristotle writes about the production and reception of sound and echoes

bull 27 ADMarcus Vitruvius Pollio De Architectura first instructions on the acoustic design of theaters

bull 800s Islamic culture produces new knowledge on sound-related phenomena(eg hearing and speech production)

bull 1500sThe effects of Renaissance cathedrals on music

Creek aκουειν = rdquoto hearrdquo

History

bull Mid 1600s

Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings

bull 1670`sFirst purpose-built concert hall is finished in London

bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework

bull 1816

P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)

History

bull Beginning of 1800s

Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms

bull 1850

Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also

bull 1860s

Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance

bull 1876

A G Bell invents the microphone (however condensator microphone is notinvented until 1916)

bull 1877

Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration

History

bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard

Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch

Sabine equation for calculating the reverberation time

bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall

bull 1920Efirst patented acoustical tile

bull 1927First anechoic chamber built (F Watson)

History

bull 1930s

First sound level meter (P Sabine)

bull 1930s

Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities

acoustics becomes a tool for humans to control the environment

bull 1943

The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established

the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s

Acoustics as a field of science and

technologybull Old field of science but significant effects not until the 20th century

bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies

ndash Hearing protection in industrial labour

ndash Privacy in residential buildings

ndash The building of spaces which work according to desired function

bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing

ndash Speech communication

ndash Music

ndash Warning signals

ndash Sound in nature

Acoustical design of buildings

rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan

estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo

Tekniikan lisensiaatti Eero Lampio 1962

The rdquofour-fieldrdquo of acoustical design

Acoustical design of buildings

(Architecturalacoustics)

Roomacoustics

Building acoustics

Noisecontrol

Vibrationisolation

The rdquofour-fieldrdquo of acoustical design

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Execution

bull Compulsory

ndash Design exercise

ndash Exam

bull Recommended and desirable

ndash Attending lectures

ndash Solving exercies independently at home

bull Course books

ndash RIL 243-1-2007 (only available in

Finnish)

ndash Master Handbook of Acoustics

EverestampPohlman (a few sections to be

notified later)

The scope of acoustics

[Lindsay 1964 muutettu]

[Lindsay`s wheel of acoustics

1964 modified Remes]

Brief history of acoustics

rdquoAcoustics is a science of the last thirty yearsrdquo

Physicist Dayton Miller 1931

History

bull 6th century BCPythagoras investigates the relation between the length and pitch of strings

bull 325 BCAristotle writes about the production and reception of sound and echoes

bull 27 ADMarcus Vitruvius Pollio De Architectura first instructions on the acoustic design of theaters

bull 800s Islamic culture produces new knowledge on sound-related phenomena(eg hearing and speech production)

bull 1500sThe effects of Renaissance cathedrals on music

Creek aκουειν = rdquoto hearrdquo

History

bull Mid 1600s

Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings

bull 1670`sFirst purpose-built concert hall is finished in London

bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework

bull 1816

P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)

History

bull Beginning of 1800s

Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms

bull 1850

Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also

bull 1860s

Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance

bull 1876

A G Bell invents the microphone (however condensator microphone is notinvented until 1916)

bull 1877

Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration

History

bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard

Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch

Sabine equation for calculating the reverberation time

bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall

bull 1920Efirst patented acoustical tile

bull 1927First anechoic chamber built (F Watson)

History

bull 1930s

First sound level meter (P Sabine)

bull 1930s

Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities

acoustics becomes a tool for humans to control the environment

bull 1943

The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established

the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s

Acoustics as a field of science and

technologybull Old field of science but significant effects not until the 20th century

bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies

ndash Hearing protection in industrial labour

ndash Privacy in residential buildings

ndash The building of spaces which work according to desired function

bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing

ndash Speech communication

ndash Music

ndash Warning signals

ndash Sound in nature

Acoustical design of buildings

rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan

estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo

Tekniikan lisensiaatti Eero Lampio 1962

The rdquofour-fieldrdquo of acoustical design

Acoustical design of buildings

(Architecturalacoustics)

Roomacoustics

Building acoustics

Noisecontrol

Vibrationisolation

The rdquofour-fieldrdquo of acoustical design

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

The scope of acoustics

[Lindsay 1964 muutettu]

[Lindsay`s wheel of acoustics

1964 modified Remes]

Brief history of acoustics

rdquoAcoustics is a science of the last thirty yearsrdquo

Physicist Dayton Miller 1931

History

bull 6th century BCPythagoras investigates the relation between the length and pitch of strings

bull 325 BCAristotle writes about the production and reception of sound and echoes

bull 27 ADMarcus Vitruvius Pollio De Architectura first instructions on the acoustic design of theaters

bull 800s Islamic culture produces new knowledge on sound-related phenomena(eg hearing and speech production)

bull 1500sThe effects of Renaissance cathedrals on music

Creek aκουειν = rdquoto hearrdquo

History

bull Mid 1600s

Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings

bull 1670`sFirst purpose-built concert hall is finished in London

bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework

bull 1816

P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)

History

bull Beginning of 1800s

Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms

bull 1850

Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also

bull 1860s

Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance

bull 1876

A G Bell invents the microphone (however condensator microphone is notinvented until 1916)

bull 1877

Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration

History

bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard

Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch

Sabine equation for calculating the reverberation time

bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall

bull 1920Efirst patented acoustical tile

bull 1927First anechoic chamber built (F Watson)

History

bull 1930s

First sound level meter (P Sabine)

bull 1930s

Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities

acoustics becomes a tool for humans to control the environment

bull 1943

The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established

the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s

Acoustics as a field of science and

technologybull Old field of science but significant effects not until the 20th century

bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies

ndash Hearing protection in industrial labour

ndash Privacy in residential buildings

ndash The building of spaces which work according to desired function

bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing

ndash Speech communication

ndash Music

ndash Warning signals

ndash Sound in nature

Acoustical design of buildings

rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan

estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo

Tekniikan lisensiaatti Eero Lampio 1962

The rdquofour-fieldrdquo of acoustical design

Acoustical design of buildings

(Architecturalacoustics)

Roomacoustics

Building acoustics

Noisecontrol

Vibrationisolation

The rdquofour-fieldrdquo of acoustical design

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

[Lindsay 1964 muutettu]

[Lindsay`s wheel of acoustics

1964 modified Remes]

Brief history of acoustics

rdquoAcoustics is a science of the last thirty yearsrdquo

Physicist Dayton Miller 1931

History

bull 6th century BCPythagoras investigates the relation between the length and pitch of strings

bull 325 BCAristotle writes about the production and reception of sound and echoes

bull 27 ADMarcus Vitruvius Pollio De Architectura first instructions on the acoustic design of theaters

bull 800s Islamic culture produces new knowledge on sound-related phenomena(eg hearing and speech production)

bull 1500sThe effects of Renaissance cathedrals on music

Creek aκουειν = rdquoto hearrdquo

History

bull Mid 1600s

Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings

bull 1670`sFirst purpose-built concert hall is finished in London

bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework

bull 1816

P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)

History

bull Beginning of 1800s

Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms

bull 1850

Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also

bull 1860s

Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance

bull 1876

A G Bell invents the microphone (however condensator microphone is notinvented until 1916)

bull 1877

Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration

History

bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard

Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch

Sabine equation for calculating the reverberation time

bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall

bull 1920Efirst patented acoustical tile

bull 1927First anechoic chamber built (F Watson)

History

bull 1930s

First sound level meter (P Sabine)

bull 1930s

Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities

acoustics becomes a tool for humans to control the environment

bull 1943

The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established

the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s

Acoustics as a field of science and

technologybull Old field of science but significant effects not until the 20th century

bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies

ndash Hearing protection in industrial labour

ndash Privacy in residential buildings

ndash The building of spaces which work according to desired function

bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing

ndash Speech communication

ndash Music

ndash Warning signals

ndash Sound in nature

Acoustical design of buildings

rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan

estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo

Tekniikan lisensiaatti Eero Lampio 1962

The rdquofour-fieldrdquo of acoustical design

Acoustical design of buildings

(Architecturalacoustics)

Roomacoustics

Building acoustics

Noisecontrol

Vibrationisolation

The rdquofour-fieldrdquo of acoustical design

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Brief history of acoustics

rdquoAcoustics is a science of the last thirty yearsrdquo

Physicist Dayton Miller 1931

History

bull 6th century BCPythagoras investigates the relation between the length and pitch of strings

bull 325 BCAristotle writes about the production and reception of sound and echoes

bull 27 ADMarcus Vitruvius Pollio De Architectura first instructions on the acoustic design of theaters

bull 800s Islamic culture produces new knowledge on sound-related phenomena(eg hearing and speech production)

bull 1500sThe effects of Renaissance cathedrals on music

Creek aκουειν = rdquoto hearrdquo

History

bull Mid 1600s

Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings

bull 1670`sFirst purpose-built concert hall is finished in London

bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework

bull 1816

P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)

History

bull Beginning of 1800s

Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms

bull 1850

Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also

bull 1860s

Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance

bull 1876

A G Bell invents the microphone (however condensator microphone is notinvented until 1916)

bull 1877

Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration

History

bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard

Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch

Sabine equation for calculating the reverberation time

bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall

bull 1920Efirst patented acoustical tile

bull 1927First anechoic chamber built (F Watson)

History

bull 1930s

First sound level meter (P Sabine)

bull 1930s

Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities

acoustics becomes a tool for humans to control the environment

bull 1943

The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established

the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s

Acoustics as a field of science and

technologybull Old field of science but significant effects not until the 20th century

bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies

ndash Hearing protection in industrial labour

ndash Privacy in residential buildings

ndash The building of spaces which work according to desired function

bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing

ndash Speech communication

ndash Music

ndash Warning signals

ndash Sound in nature

Acoustical design of buildings

rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan

estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo

Tekniikan lisensiaatti Eero Lampio 1962

The rdquofour-fieldrdquo of acoustical design

Acoustical design of buildings

(Architecturalacoustics)

Roomacoustics

Building acoustics

Noisecontrol

Vibrationisolation

The rdquofour-fieldrdquo of acoustical design

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

History

bull 6th century BCPythagoras investigates the relation between the length and pitch of strings

bull 325 BCAristotle writes about the production and reception of sound and echoes

bull 27 ADMarcus Vitruvius Pollio De Architectura first instructions on the acoustic design of theaters

bull 800s Islamic culture produces new knowledge on sound-related phenomena(eg hearing and speech production)

bull 1500sThe effects of Renaissance cathedrals on music

Creek aκουειν = rdquoto hearrdquo

History

bull Mid 1600s

Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings

bull 1670`sFirst purpose-built concert hall is finished in London

bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework

bull 1816

P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)

History

bull Beginning of 1800s

Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms

bull 1850

Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also

bull 1860s

Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance

bull 1876

A G Bell invents the microphone (however condensator microphone is notinvented until 1916)

bull 1877

Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration

History

bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard

Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch

Sabine equation for calculating the reverberation time

bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall

bull 1920Efirst patented acoustical tile

bull 1927First anechoic chamber built (F Watson)

History

bull 1930s

First sound level meter (P Sabine)

bull 1930s

Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities

acoustics becomes a tool for humans to control the environment

bull 1943

The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established

the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s

Acoustics as a field of science and

technologybull Old field of science but significant effects not until the 20th century

bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies

ndash Hearing protection in industrial labour

ndash Privacy in residential buildings

ndash The building of spaces which work according to desired function

bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing

ndash Speech communication

ndash Music

ndash Warning signals

ndash Sound in nature

Acoustical design of buildings

rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan

estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo

Tekniikan lisensiaatti Eero Lampio 1962

The rdquofour-fieldrdquo of acoustical design

Acoustical design of buildings

(Architecturalacoustics)

Roomacoustics

Building acoustics

Noisecontrol

Vibrationisolation

The rdquofour-fieldrdquo of acoustical design

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

History

bull Mid 1600s

Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings

bull 1670`sFirst purpose-built concert hall is finished in London

bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework

bull 1816

P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)

History

bull Beginning of 1800s

Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms

bull 1850

Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also

bull 1860s

Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance

bull 1876

A G Bell invents the microphone (however condensator microphone is notinvented until 1916)

bull 1877

Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration

History

bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard

Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch

Sabine equation for calculating the reverberation time

bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall

bull 1920Efirst patented acoustical tile

bull 1927First anechoic chamber built (F Watson)

History

bull 1930s

First sound level meter (P Sabine)

bull 1930s

Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities

acoustics becomes a tool for humans to control the environment

bull 1943

The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established

the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s

Acoustics as a field of science and

technologybull Old field of science but significant effects not until the 20th century

bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies

ndash Hearing protection in industrial labour

ndash Privacy in residential buildings

ndash The building of spaces which work according to desired function

bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing

ndash Speech communication

ndash Music

ndash Warning signals

ndash Sound in nature

Acoustical design of buildings

rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan

estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo

Tekniikan lisensiaatti Eero Lampio 1962

The rdquofour-fieldrdquo of acoustical design

Acoustical design of buildings

(Architecturalacoustics)

Roomacoustics

Building acoustics

Noisecontrol

Vibrationisolation

The rdquofour-fieldrdquo of acoustical design

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

History

bull Beginning of 1800s

Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms

bull 1850

Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also

bull 1860s

Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance

bull 1876

A G Bell invents the microphone (however condensator microphone is notinvented until 1916)

bull 1877

Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration

History

bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard

Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch

Sabine equation for calculating the reverberation time

bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall

bull 1920Efirst patented acoustical tile

bull 1927First anechoic chamber built (F Watson)

History

bull 1930s

First sound level meter (P Sabine)

bull 1930s

Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities

acoustics becomes a tool for humans to control the environment

bull 1943

The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established

the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s

Acoustics as a field of science and

technologybull Old field of science but significant effects not until the 20th century

bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies

ndash Hearing protection in industrial labour

ndash Privacy in residential buildings

ndash The building of spaces which work according to desired function

bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing

ndash Speech communication

ndash Music

ndash Warning signals

ndash Sound in nature

Acoustical design of buildings

rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan

estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo

Tekniikan lisensiaatti Eero Lampio 1962

The rdquofour-fieldrdquo of acoustical design

Acoustical design of buildings

(Architecturalacoustics)

Roomacoustics

Building acoustics

Noisecontrol

Vibrationisolation

The rdquofour-fieldrdquo of acoustical design

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

History

bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard

Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch

Sabine equation for calculating the reverberation time

bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall

bull 1920Efirst patented acoustical tile

bull 1927First anechoic chamber built (F Watson)

History

bull 1930s

First sound level meter (P Sabine)

bull 1930s

Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities

acoustics becomes a tool for humans to control the environment

bull 1943

The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established

the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s

Acoustics as a field of science and

technologybull Old field of science but significant effects not until the 20th century

bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies

ndash Hearing protection in industrial labour

ndash Privacy in residential buildings

ndash The building of spaces which work according to desired function

bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing

ndash Speech communication

ndash Music

ndash Warning signals

ndash Sound in nature

Acoustical design of buildings

rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan

estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo

Tekniikan lisensiaatti Eero Lampio 1962

The rdquofour-fieldrdquo of acoustical design

Acoustical design of buildings

(Architecturalacoustics)

Roomacoustics

Building acoustics

Noisecontrol

Vibrationisolation

The rdquofour-fieldrdquo of acoustical design

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

History

bull 1930s

First sound level meter (P Sabine)

bull 1930s

Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities

acoustics becomes a tool for humans to control the environment

bull 1943

The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established

the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s

Acoustics as a field of science and

technologybull Old field of science but significant effects not until the 20th century

bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies

ndash Hearing protection in industrial labour

ndash Privacy in residential buildings

ndash The building of spaces which work according to desired function

bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing

ndash Speech communication

ndash Music

ndash Warning signals

ndash Sound in nature

Acoustical design of buildings

rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan

estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo

Tekniikan lisensiaatti Eero Lampio 1962

The rdquofour-fieldrdquo of acoustical design

Acoustical design of buildings

(Architecturalacoustics)

Roomacoustics

Building acoustics

Noisecontrol

Vibrationisolation

The rdquofour-fieldrdquo of acoustical design

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Acoustics as a field of science and

technologybull Old field of science but significant effects not until the 20th century

bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies

ndash Hearing protection in industrial labour

ndash Privacy in residential buildings

ndash The building of spaces which work according to desired function

bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing

ndash Speech communication

ndash Music

ndash Warning signals

ndash Sound in nature

Acoustical design of buildings

rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan

estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo

Tekniikan lisensiaatti Eero Lampio 1962

The rdquofour-fieldrdquo of acoustical design

Acoustical design of buildings

(Architecturalacoustics)

Roomacoustics

Building acoustics

Noisecontrol

Vibrationisolation

The rdquofour-fieldrdquo of acoustical design

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Acoustical design of buildings

rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan

estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo

Tekniikan lisensiaatti Eero Lampio 1962

The rdquofour-fieldrdquo of acoustical design

Acoustical design of buildings

(Architecturalacoustics)

Roomacoustics

Building acoustics

Noisecontrol

Vibrationisolation

The rdquofour-fieldrdquo of acoustical design

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

The rdquofour-fieldrdquo of acoustical design

Acoustical design of buildings

(Architecturalacoustics)

Roomacoustics

Building acoustics

Noisecontrol

Vibrationisolation

The rdquofour-fieldrdquo of acoustical design

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

The rdquofour-fieldrdquo of acoustical design

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Room acoustics

bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo

Engineer U Varjo 1938

bull The reflection attennuation and propagation of sound in a space

bull Goal sound (speech orchestra etc) soundsas is required by the use of space

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Building acoustics 13

bull Transition of sound between spaces via structuresndash Not only through the

separating structure butalso as flankingtransmission and throughholes etc

bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation

ndash Impact sound insulation

ndash Structure-borne sound insulation

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Building acoustics 23

bull Sound insulationndash Between spaces

(airborne and impact)

ndash From inside to outside and viceversa

ndash Equipment noise

ndash Vibration

bull Choosing the construction type is also acoustic design

Rakenteiden

ilmaaumlaumlneneristaumlvyyksiauml

0

5

10

15

20

25

30

35

40

45

50

50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

Taajuus [Hz]

R [d

B]

Kipsilevy 2 x 13 mm (18 kgm2)

Puu 50 mm (25 kgm2)

Kevytbetoni 68 mm (27 kgm2)

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Building acoustics 33

bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures

bull Speech is airborne soundbull Sounds caused by walking or

dropping objects on the floor areimpact sound (askelaumlaumlni)

bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure

bull All technical equipment produce bothairborne and structure-borne sound

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Noise control 12

bull Outdoor noise sources

road railway and

airplane traffic

bull Indoor noise sources

machinery and service

equipment (talotekniikka)

bull Goal to diminish the

production and

propagation of noise

Kuva Salter 1999

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Noise control 22

bull HVAC equipmentndash outdoors

ndash indoors

bull Traffic noisendash Road traffic

ndash Railway traffic

ndash Airplane traffic

bull Machinery industry

bull Measurement of noiseemission

bull Noise modelling

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Vibration isolation 12

rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml

naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta

kuten kipinoumliden tuhkan noen savun

laumlmmoumln loumlyhkaumln kaasujen houmlyryn

taumlrinaumln jyskeen taikka muun sellaisen kauttardquo

Laki eraumlistauml naapuruussuhteista 1920

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Vibration isolation 22

bull All machinery in

contact with the

building frame vibrate

and produce sound

bull Goal to diminish the

propagation of the

vibration energy by

isolating the machine

from the building

frame using elastic

building elements

Saumlhkoumljohto vapaasti riippuvana lenkkinauml

PallotasainPallotasain

BetonimassaTaumlrinaumlneristimet

Betonilaatta 250 mm

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Goals os acoustical design

bull Suitability to intended usendash Suitability to speech music

ndash Appropriate sound insulationbetween spaces

bull Healthinessndash Hearing lossndash Acoustic ergonomy

bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and

aesthetics

bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010

Lassila Hirvilammi Arkkitehdit

Helimaumlki Acoustics

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Significance of acoustical design 13

bull The starting points of acoustic design

1 Healthiness

2 Comfort

3 Use of space

bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration

bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Significance of acoustical design 23

bull Sound constitutes a significant part of the human

sensory environment

bull Noise (rdquounwanted soundrdquo) has significant physiological

anf psychological effects on humans

ndash Research has been extensive from the beginning if the 20th

century

ndash The effects of noise are not limited to loud noise (hearing

damage risk) but also a quiet sound can be perceived as noise

if it for example hinders concentration

bull Bad acoustics also has economic consequences

Akustiikka 1011

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Significance of acoustical design 33Investing in acoustics is worth it

bull A space which does not function acoustically as required byits use is a stranded investment ie bad business

bull Improving the acoustical conditions in a finished building is always expensivendash Meetings

ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem

ndash Larger design costsndash Larger building costs

bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions

ndash There is no need to do changes to a space which works as intended

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Regulations and instruction in acoustics

bull The National Building Code of Finland Section C1-1998

bull The National Building Code of Finland Section D2-2010

bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health

bull Government Decision on the Noise Level Guide Values (9931992)

bull Acoustic Clasification of Spaces in Buildings standard SFS 5907

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Acoustics in the building project

Acoustics should be considered in the building project as soon

as possible ndash the sooner the more demanding the project is

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Acoustics in the building project Project planning phase (hankesuunnittelu)

bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces

bull Room acousticsndash Use of space surface area volume shape room acoustical

materials

bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)

positioning of engine rooms and noisy machinery

bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of

buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)

ndash Vibration surveys

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Acoustics in the building project Preliminary design phase (luonnossuunnittelu)

bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation

requirements of doors floor coverings

bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements

as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration

bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of

how the target values can be fulfilled selection of sewer system

bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony

glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient

sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)

Cost for the project

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Acoustics in the building project Implementation planning phase (toteutus-) 13

bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering

windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed

ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)

bull Sound insulationndash Presentation of the details of structural joints for the structural designer

drawing of details if needed

ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements

bull Room acousticsndash Positioning of room acoustical materials in different spaces to the

architect approval of furnishings etc selected by the interior designer

ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Acoustics in the building project Implementation planning phase (toteutus-) 23

bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop

calculations equipment lists HVAC drawings and noise data on all equipment fans etc

ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers

ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)

ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets

All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Acoustics in the building project Implementation planning phase (toteutus-) 33

bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint

bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building

sitendash Changes due to selection of HVAC equipment (typically affect

the design of silencers)ndash Inspection of vibration isolators

bull Site supervision and inspection visits in demanding projects

bull Control measurements

Implementation according to plans

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound as a physical phenomenon

basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja

vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo

Yli-insinoumloumlri Paavo Arni 1949

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

What is sound

bull Changes in air pressure in relation to static air pressure

bull In air sound propagates as longitudinal wave motion

Kuvat Everest amp Pohlman 2011

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound pressure level (SPL)

bull Sound pressure p = change in air pressure in relation to

static air pressure (ca 100 kPa)

bull Smallest detectable sound pressure p0 = 20 μPa

bull Sound pressure corresponding to treshold of pain 20

Pa

bull Sound pressure level [dB]

0

2

0

2

lg20lg10p

p

p

pLp

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Frequency and wavelength

bull Frequency f [Hz] = number of

vibrations per time unit

bull Normal hearing range ca 20 ndash

20000 Hz

bull Relation between frequency and

wavelength

bull c = speed of sound

(343 ms in air T = 20 degC)

Kuva Hongisto 2011

f

ccf

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Frequency ranges in acoustics

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

The function of ear

[Egan 2007]

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sensitivity of hearing

rdquoequal loudness contoursrdquo

(ISO 226)

Hearing

treshold

Sensitivity of hearing to

different frequencies is

not constant

Must be considered

when eg evaluating the

noise annoyance

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Frequency bandsOctave bands

0

20

40

60

80

100

120

16 315 63 125 250 500 1000 2000 4000 8000 16000

Oktaavikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Frequency bands One-third octave bands

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

A-weighting

-80

-60

-40

-20

0

20

40

60

80

100

120125 16

20

25

315 40

50

63

80

100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

10000

12500

16000

20000

Terssikaistan keskitaajuus [Hz]

Aumlaumlnenpain

eta

so [

dB]

Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

A-weighting

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound level

bull Due to practical reasons the sound pressure level

measured in the whole frequency range using A-

weighting is usually given as a single number

bull This single number quantity is called sound level

(aumlaumlnitaso) and denoted as LA

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

S

O

U

N

D

L

E

V

E

L

S

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Equivalent and maximum sound level

bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously

both long-term equivalent (= average) and instantaneousmaximum sound level must be considered

bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the

average sound level during the investigated time period T

bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period

i

L

iiAT

TL

10

TeqA10

1lg10

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Addition of sound levels

bull Generally for two sound sources (Lp1 ja Lp2)

bull For N sound sources

bull The formulas apply to non-correlating sound sources

ie when the phases of the sound waves are

independent of each other this condition is true for all

every-day sound sources

1010 21

1010lg10 pp

totp

LLL

N

n

L np

totpL

1

10

10lg10

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Addition of sound levels

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Addition of sound levels

bull If the difference between sound levels exceeds 10 dB

the louder sound practically determines the total sound

level

[Figure Hongisto 2011]

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound power level (aumlaumlnitehotaso)

bull Sound power W [W] = the ability of a sound source to produce sound

bull Sound power corresponding to hearing treshold W0 = 1 pW

bull Sound power level LW [dB]

bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source

bull Note Sound power level is a property of the sound sourceand does not depend on the environment

0

lg10W

WLW

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound intensity level (intensiteettitaso)

bull Sound intensity I [Wm2] = power per unit area

bull Intensity corresponding to hearing treshold 1 pWm2

bull Sound intensity level

bull The relation between sound intensity and power

where S is surface area [m2]

0

lg10I

ILI

ISW

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Measurement of sound power level

bull Sound power level can be determied by measuring the

average intensity level at a surface enveloping the

sound source

mikrofoni

lattiamaa

aumlaumlnilaumlhde

SLL IW lg10

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound propagation and attenuationSpherical wave

In a spherical

wave the sound

power of a point

source spreads

over the surface

area of a sphere

Kuva Salter et al 1999

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound propagation and attenuationSound divergence in a free field

bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)

where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source

bull When Ω = 4π (spherical wave) and k = 1 we get

in a spherical wave Lp decreases 6 dB with doubling of distance

k

rLL Wp

2

lg10

11lg204lg10 2 rLrLL WWp

distance attenuation

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound propagation and attenuationEffect of location

bull The effect of location of the source (ie solid angle Ω)

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Distance attenuation in spherical wavea)

b)

c)

Spherical wave

Distance x 2 Lp - 6 dB

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Distance attenuation in cylidrical wave

Cylindrical wave

Distance x 2 Lp - 3 dB

a)

b)

c)

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound propagation and attenuationDirectivity factor

bull Definition of directivity factor k

meaning directivity factor at angle θ = sound intensity at

angle θ average intensity of sound source radiated to

all directions

bull Determining the directivity of a sound source is difficult

thus directivity information of eg HVAC equipment is

rarely available

sound sources are typically treated as point sources

(k = 1 no directivity)

kI

Ik

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound absorption

bull The sound absorption coefficient (absorptiosuhde)

describes the ability of a material to absorb sound power

bull Sound absorption coefficient α is defined as the sound

power incident on a surface W1 divided by the sound

power that is not reflected from the surface W1 ndash W2

W

W

1

2

1

21

W

WW α = 01

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Measurement of absorption coefficient

bull Absorption coefficient is a frequency-dependentquantity

bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber

(ISO 354)

bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound absorption vs sound insulation

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound absorption vs sound insulationReflection - transmission

bull Reflection

ndash Large value sound absorbed

ndash Small value sound reflected

i

ri

W

WW

i

t

W

W

α = 01

τ = 01

bull Transmission

ndash Large value most of the sound energy penetrates the structure

ndash Small value sound reflected

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound absorption vs sound insulationReflection - transmission

bull Attenuation of sound hitting a

surface as a function of

absorption coefficient

bull Attenuation of sound penetrating

the structure as a function of

transmission coefficient

1lg10D

t

i

W

WR lg10

1lg10

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Reverberation time

bull The time it takes for sound pressure level to decrease

60 dB after the sound source has been switched off

bull Measurement of reverberation time using the impulse

method

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Reverberation time

bull Reverberation time is

calculated using the

Sabine equation

bull Other formulae also

exist

A

VT 160

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Reverberation timeDiffuse sound field

bull Sabine equation assumes a diffuse sound field in the

room

bull Diffuse sound field equal sound pressure level at each

point in the room

ndash Condition is satisfied in cubic spaces with dimensions gtgt sound

wavelength and with hard sound reflecting surfaces

ndash Condition is not satisfied is the space is large and highly

absorbing or if all the absorptio material is situated on one

surface while the other surfaces are sound reflecting

bull Sabine equation can however be applied in most

spaces with sufficient accuracy

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound absorption area

bull Absorption area in Sabine equation A [m2] depends on

ndash Sound absoprtion coefficients of materials α

ndash Surface areas S of materials in the room

bull Total sound absorption area

bull Note Aabsorption area and reverberation time are

frequency-dependent quantities

i

n

1i

inn2211 SSSSA

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Examples of reverberation time

Tila Jaumllkikaiunta-aika T [s]

02 shellip03 s Aumlaumlnitarkkaamo

03 shellip08 s Elokuvateatteri

05 s Kalustettu makuuhuone

05 shellip08 s Hyvin suunniteltu luokkahuone

10 shellip12 s Teatteri suuri auditorio

15 s Kalustamaton makuuhuone

18 s Tampere-talon iso sali

2 shellip3s Suuri aula jossa ei vaimennusta

5 s Tampereen tuomiokirkko tyhjaumlnauml

95 s Helsingin rautatieasema

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound field in a room

Direct

sound

Reverberant

sound

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Room attenuation (huonevaimennus)

bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation

bull The latter term is called room attenuation(huonevaimennus)

bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field

bull Notendash A gt 4 m2

positive room attenuation (sound attenuates)

ndash A lt 4 m2 negative room attenuation (sound amplified)

4lg10

ALL wp

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Room attenuation

bull Room attenuation

4lg10

A

The absorption area

and room attenuation

of a typical furnished

room

10 m2 4 dB

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Significance of room attenuation

bull The sound level caused by a sound source depends

highly on the amount of room attenuation

must be considered eg in HVAC noise control

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound field in enclosed spaces

bull Sound pressure level in an enclosed space

Ar

kLL Wp

4lg10

2

Property of

sound source

Direct

sound

Reverberant

sound

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound field in enclosed spacesReverberation radius

bull Sound level in a room reaches a certain constant level a

few meters from the sound source

bull This distance is called reverberation radius

(kaiuntasaumlde) = the distance from the sound source at

which the level of direct and reverberant sound are

equal

4

kArk

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]

20

30

40

50

60

70

80

01 1 10 100

Etaumlisyys aumlaumlnilaumlhteeseen r [m]

Diffuusi huone yhtaumllouml (420) DL2=0 dB

Avotoimisto huono vaimennus DL2=5 dB

Avotoimisto hyvauml vaimennus DL2=11 dB

Heijastukseton tila (tai ulkona)

DL2 saadaan jyrkkyydestauml

r1=2 m ja L1=53 dB

r2=4 m ja L2=42 dB

DL2=11 dB

reverberation radius

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta

Characteristics of human speech

normaali korotettu voimakas

Hz dB dB dB

250 572 615 640

500 598 656 703

1k 535 623 706

2k 488 568 659

4k 438 513 599

8k 386 426 489

A 595 665 737

Lin 626 687 747

Aumlaumlnitaso [dB]

0

20

40

60

80

250 500 1k 2k 4k 8k

Taajuus [Hz]

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

pystysuunta

Suhteellinen aumlaumlnitaso [dBA]

-10

-8

-6

-4

-2

0

2

490

80 7060

50

40

30

20

10

0

350

340

330

320

310300

290280270

260250240

230

220

210

200

190

180

170

160

150

140

130120

110100

vaakasuunta