31-10-12 Edu Set Sound Insulation & Acoustics

8/14/2019 31-10-12 Edu Set Sound Insulation & Acoustics

1/81


2/81

GENERAL INTRODUCTION Sound is generated in the air when a surface is

vibrated.

The vibrating surface sets up waves of compressionand rarefaction.

To understand it let us take example of tuning fork

2PRESENTATION BY MANISH KUMAR LEC.ARCHITECTURE AT PATIALA


3/81

GENERAL INTRODUCTIONI have drawn three pictures of a

tuning fork to help you visualize

how air molecules might look

around a tuning fork.

When the tuning fork is at rest,

the fork is surrounded by

molecules in the air.



4/81

GENERAL INTRODUCTIONAs a tuning fork's prongs move

apart because of a vibration.

The molecules ahead of it are

crowded together.

They look like they are being

pushed together. They bump

each other.



5/81

GENERAL INTRODUCTIONAs the tuning fork's prongs

come back together, it leaves a

region that has fewer

molecules than usual.The region of a sound wave in

which the molecules are

crowded together is a

compression.

The region of a sound wave in

which particles are spread

apart is a rarefaction.



6/81

GENERAL INTRODUCTIONAs a tuning fork vibrates, it causes molecules in

the air to move.

The molecules bump into other moleculesnearby, causing them to move.

This process continues from molecule tomolecule.

The result is a series of compressions andrarefactions that make up sound waves.



7/81

GENERAL INTRODUCTIONAnd these compression and rarefactions sets the

ear drum vibrating.

The movements of ear drum are translated by the

brain into sound sensation.

So, we really don't hear with our ears - we hear

with our brains!



8/81

GENERAL INTRODUCTIONShape (dish

type) of theouter ear ishelpful in

receivingsound waves.



9/81

GENERAL INTRODUCTIONHere's How It Works Sound vibrations, or sound waves, are collected by

the OUTER EAR.

And travel into the ear canal, where they bump upagainst the ear drum.

The EAR DRUM vibrates in sympathy with these

sound waves. As it vibrates, it moves a series of tiny bones in

the MIDDLE EAR



10/81


11/81

GENERAL INTRODUCTION



12/81


13/81


14/81

Intensity and loudness of sound Loudness of a sound corresponds to the degree of

sensation depending upon the intensity of sound and

sensitivity of ear drums.

It may also happen that the same listener might give

different judgments about the loudness of sound of

the same intensity but of different frequencies as the

response of the ear is found to vary with the frequency

of vibration.



15/81

Frequency and pitch of sound

Frequency or pitch is defined as the number of cycle

which a sounding body makes in each unit of time.

It is measure of the quality of sound. The sensation of pitch depends upon the frequency

with which the vibrations succeed one another at the

ear.

Greater the frequency the higher the pitch.

And the lesser the frequency the lower the pitch.



16/81

Frequency and pitch of sound The audio range falls between 20 Hz and 20,000 Hz. This

range is important because its frequencies can be detected

by the human ear. A frequency is expressed in terms of Hz(Hertz)

and it determines pitch of sound source. They can be

categorized as:

Low tones sound of urban road traffic.

Mild tones sound of piano notes.

High tones sound of single tea kettle.



17/81


18/81

The behavior of sound propagationIt is affected by many things:

The speed of sound within the medium depends upon

temperature of the medium ,which in turns effect thedensity and pressure of the medium..

The propagation is also affected by the motion of the

medium itself. For example, sound moving through wind is further

transported towards the direction of wind.



19/81

The behavior of sound propagation The viscosity of the medium also affects the

motion of sound waves.

It determines the rate at which sound is

attenuated.

For many media, such as air or water, attenuationdue to viscosity is negligible.

Sound cannot travel through a vacume.



20/81

The behavior of sound propagation

It travels much faster in solids and liquids then inair.

The velocity of sound in atmospheric air at 20

degree centigrade is 343 meter per second. The velocity of sound in pure water is 1450 meter

per second.

The velocity of sound in bricks is 4300 meter persecond.

The velocity of sound in concrete is 4000 meterper second.



21/81

The behavior of sound in enclosures

When the sound waves strike the surfaceof room three things happen

(1) Some of the sound is reflected back in the room.

(2) Some of the sound energy is absorbed by the

surfaces and listeners of the room/hall .

(3) And some of the sound is transmitted out of the

room through vibrations of f loors, walls and

ceilings.



22/81

The behavior of sound in enclosures

The amount of sound reflected and absorbed

depends upon the different surfaces of room.

And the sound transmitted outside the room will

depend upon .

The sound insulation properties of walls , f loors

and ceiling etc. .



23/81

Reflection of sound waves.

Reflection of sound waves is exactly the same asthat of light waves.

That is angle of incidence is equal to the angle ofreflection. *c

*c *c

INCIDENT WAVEREFLECTED WAVE

REFLECTING SURFACE.



24/81


The reflectedwave

frontfrom a flat

surface are alsospherical and their

centre of curvature

is the image of

source of sound.

FLAT REFLECTORWAVE FRONT

SOUND

SOURCE



25/81

Reflection of sound waves.Sound waves reflected ata convex surface aremagnified and areconsidered bigger.

They are attenuated andtherefore weaker.

So convex surface may beused with advantage tospread the sound wavesthroughout the room.

WAVE FRONT CONVEXREFLECTOR

SOUNDSOURCE



26/81


The sound waves reflected ata concave surface areconsidered smaller.

The waves are most condensedand therefore amplified.

The concave surface may beprovided for concentration ofreflected waves at certainpoints.

WAVE FRONT

CONCAVE REFLECTOR

SOUNDSOURCE



27/81

Acoustics general introduction The scientific study of the phenomenon of

sound is known as Acoustics.

Acoustics as applied to buildings is the scienceof sound which assures the optimumconditions for

Producing sound/speech/music

Listening of sound/speech/music

Recording /editing of sound etc.



28/81

Acoustical Interaction

Acoustics means to work on these threeparameters and improve sound experience.



29/81

Acoustical Interaction

Sound is attenuated by absorption Historically, the primary focus of acoustics was

the use of absorbing surfaces to control thereverberation times and loudness of spaces.

Redirected by reflection

Uniformly scattered by diffusion Good architectural acoustic design requires an

appropriate combination of absorptive,reflective and diffusive surfaces



30/81

Acoustics general introduction

For better acoustical results the construction andapplication of sound absorbents and soundreflective materials should be carefully selected

and placed.

This will help in providing better quality of audiovideo sensations to viewers/ listeners.

Proper acoustical planning can reduce orcompletely eliminate defects related to sound,which are called acoustical defects.



31/81

Acoustical defects

List of acoustical defects

Reverberation.

Formations of echoes.

Sound foci.

Dead spots.

Insufficient loudness.

Exterior noises.



32/81

Acoustical defects (Reverberation)

Reverberation is the persistence of soundin the enclosed space , after the source of

sound has stopped. Reverberant sound is the reflected sound

, as a result of improper absorption.

Reverberation may results in confusionwith the sound created next.



33/81


34/81




35/81




36/81

Reverberation time & quality of sound

Reverberation time should remain within limits as perIndian Standard Code: 2526-1963.

Sr.No.

RECOMMENDED TIME INSECONDS

ACOUSTICS

1 0.50 to 1.50 Excellent

2 1.50 to 2.00 Good

3 2.00 to 3.00 Fairly good

4 3.00 to 5.00 Bad

5 Above 5.0 seconds Very bad



37/81

Formation of echoes. Echo's

Not all sound that hits matter is absorbed. Someof it is reflected. That means sound bounces offthe solid matter the way a tennis ball bounces offa wall. Sound reflected back to its source is anecho.



38/81

Formation of echoes.

An echo is produced when the reflected sound wavereaches the ear just when the original sound from thesame source has been already heard.

Thus there is repetition of sound.

The sensation of sound persists for 1/10thof a secondafter the source has ceased.

Thus an echo must reach after 1/10th

second of thedirect sound



39/81

Formation of echoes. Multiple echoes may be heard when a sound is

reflected from a number of reflecting surfaces

placed suitably.

This defect can be removed by selecting proper

shape of the hall .

And by providing rough and porous interior

surfaces to disperse the energy of echoes.



40/81


41/81

Dead spots.

This defect is the out come of formation of soundfoci.

Because of high concentration of reflected soundat sound foci , there is deficiency of related sound

at some other points. These spots are known as dead spots where sound

intensity is so low that it is insufficient forhearing.

This defect can be removed by suitably placingdiffusers and reflectors.

Right proportions of internal spaces.



42/81

Dead spots.

Geometrical shape of roof helps in proper distribution of sound



43/81

External noise External noises from vehicles , traffic engines ,

factories , machines etc. may enter the hall either

through the openings or even through walls and otherstructural elements having improper sound

insulation.

This defect can be removed by proper planning of thehall with respect to its surroundings and by proper

sound insulation of external walls.



44/81

Acoustical design of halls The initial sound from the source should be of

adequate intensity so that it can be heard

throughout the hall .

For halls of big sizes suitable sound amplification

system should be installed.

The sound produced should be evenly distributed

so that there is no dead spots and sound foci.



45/81

Acoustical design of halls The boundary surface should be so designed that

there are no echoes or near echoes.

Desired reverberation time should be achieved by

proper placement of absorbents on wall.

The out side noise should be eliminated.



46/81

Physical Design Principles for halls



47/81




48/81




49/81




50/81




51/81




52/81




53/81

Acoustics materials

Carpet is an outstanding sound

absorptive material. When

properly selected, carpet absorbs

airborne noise as efficiently as

many specialized acoustical

materials. No other acoustical

material performs the dual role of a

floor covering and a versatile

acoustical aid.



54/81

Acoustics materials

QUIET BARRIER HDA flexible, 2lb per sq./ft. 1/4in. thick, high density

material with a smoothsurface designed to reducenoise transmission betweentwo spaces. Applicationsinclude reducing airborne

noise transmission throughwalls, ceilings and floors

http://www.soundprooffoam.com/quiet-barrier.html


55/81

Acoustics materialsQUIET BARRIER MD

A flexible, 1lb per sq./ft. 1/8 in.

thick, high density material

with a smooth surface

specially engineered to

reduce noise transmission

between two spaces.

http://www.soundprooffoam.com/econo-barrier.html


56/81


57/81

Acoustics materialsTough core Ceiling Tiles

High-performance composite

ceiling panel. Especially well-

suited to minimize sound

transmission between adjacent

spaces sharing a common attic

space. Available in a variety of

finish options and edge details.

http://www.soundprooffoam.com/tufcore-ceiling-tiles.html


58/81

Acoustics materials

Isotrax

Complete soundproofing

system for walls and

ceilings. Blocks andisolates sound, reduces

noise from traveling

through building materials.

New or existingconstruction.

http://www.soundprooffoam.com/isotrax.html


59/81

Acoustics materials

damping tiles used for noise absorption.



60/81

Sound insulation general introduction

Unwanted sound reaching the ears is called

NOISE.

It may be due to frequency of sound.

It may be due to intensity of sound .

Or it may be due to the combination of both

frequency and intensity of sound.



61/81

PRESENTATION BY MANISH KUMAR LEC.ARCHITECTURE AT PATIALA 61

Sound insulation


62/81

Sound insulation general introduction

So sound insulation is the measure by whichtransmission of sound / noise from inside to out side(vice versa ) or from one room to other is prevented.



63/81

Sound insulation ( effects of noise) It creates discomfort.

It has adverse effect on blood pressure , sleep andcauses muscular strains.

It leads to fatigue and decreases the efficiency of aperson.

It takes away essence of music and speech.

It disturbs concentration.

Prolonged exposure to noise may result in temporarydeafness or even nervous breakdown.



64/81

Classification of noise.From the origin point of view noise may be of two

types:-

Out door noise.

Indoor noise.

And noise may also be classified as

Air borne noise or sound

Structure borne noises or impact noises or sounds.



65/81

Sources of out door noises.

OUT DOOR NOISES ARE CAUSED BY:-

Road traffic.

Railways.

Climatic conditions.

Aero planes.

Moving machines.

Machines in nearby factories or buildings etc.



66/81


67/81

Transmission loss (TM) of sound

When sound is transmitted from source ororigin to the adjoining room/ area, reductionin sound intensity takes place.This is known as transmission loss (TM)Measured in decibels (dB)

60 decibels 40 decibels

TM=60-40=20 DECIBELS.



68/81


69/81


70/81

Types of sound insulating materials

Non porous rigid.

Porous rigid materials.

Non rigid porous flexible materials.



71/81

Types of sound insulating materials Non porous rigid

Brick masonry plastered on both sides

Stone masonry structures

Concrete structures RCC Structures

Porous rigid materials.

Light weight concrete

Cellular concrete

Gypsum board partitions



72/81


Non rigid porous flexible materials

Perforated boards

Compressed fiber boards

Pulp boards

Mineral wool boards

Acoustic tiles /sheets

Glass wool



73/81


Non rigid porous flexible materials

Cobalt quilt

Wood wool boards

Curtains

Foams

Celotex boards

Cane fiber etc.



74/81

Sound insulating techniquesThere are some construction techniques also which

are adopted for sound insulation.

Double wall construction.

Cavity wall construction. False ceiling.

Hollow block construction.

Double pane windows. Baffle blocks, honey combs etc.



75/81

Sound insulating techniques Double wall construction .

BOARDS WOODENSTUDS

SOUND ABSORBING BLANKETBOARDS

WOODEN STUDS



76/81


77/81

Sound insulating techniques False ceiling.

REINFORCED CONCRETE ROOF

SUSPENDERS

FALSE CEILING



78/81

Sound insulating techniques Hollow block construction.

COMPRESSED CONCRETE HOLLOW BLOCKS

HOLLOW



79/81


80/81


81/81

Thank you and enjoy sound

Documents

31-10-12 Edu Set Sound Insulation & Acoustics