Broadcast Final Design

8/2/2019 Broadcast Final Design

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I. IntroductionReverberation rooms are important tools in acoustics, used in a variety of standardized measurements, in

measuring the absorption of materials, the sound power of noise sources, and the transmission loss of partitions.

They are also used for testing satellite structures at high sound pressure levels. The study of sound fields in lightly

damped enclosed spaces can be approached in, at least, two completely different ways. One can solve the wave

equation with the prescribed boundary conditions either analytically or using numerical methods.

This approach, which is particularly useful at low frequencies, leads to a description in terms of the modes of the

room. Alternatively the problem can be studied using statistical considerations. The second approach, which is

particularly appropriate at medium and high frequencies, has the advantage of requiring far less detailed knowledge

of the geometry of the room under study, but the resulting model is not very accurate at low frequencies. According to

this (BLIND ESTIMATION OF REVERBERATION TIME BASED ON THE DISTRIBUTION OF SIGNAL DECAY

RATES) article it states that the problem of reverberation is important for both the audio signal processing and room

acoustics community. Reverberation is caused by the multi-path propagation of acoustic signals from a source to a

microphone.

Reverberant speech can be described as sounding distant with noticeable echo and colouration. The human

auditory system is believed to have echo suppression and dereverberation capabilities, which are not present when

sound is captured by microphones, such as in hands-free telecommunication devices. The characteristics of

reverberation can be derived from the room impulse response (RIR), such as reverberation time (RT), definition

(Deutlichkeit), clarity index, and the centre time. There are also signal dependent approaches, e.g., the modulation

transfer function (MTF) and the speech transmission index (STI). In particular, the reverberation time is still

considered as the objective quantity in room acoustics.

Provided an empirical formula to predict the RT in an enclosure. The formula is based solely on the geometry

and the surface material of the environment. Other methods measure the RT by analysing the decay rate of the

sound decay curve. The decay curve can be observed when an excitation signal is switched off after reaching a

steady-state sound level in the enclosure. This method is also known as the Interrupted Noise Method (ISO 3382).


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Schroeder developed a method to calculate the ensemble average of the decay curves directly using backwards

integration of the related RIR. Semi-blind methods have been developed, where the characteristics of the enclosures

are learned using neural network approaches another method is segments speech to detect gaps in sound so as to

allow the sound decay curve to be tracked. An essential tool for the study of reverberation is a method to estimate

reverberation characteristics from the microphone signal alone, such as that proposed in.

In, Ratnam develops a truely blind method for estimating the RT using a maximum-likelihood procedure. The

estimates are obtained continuously and an ordered statistics filters is used to extract the most likely RT from the

accumulated estimates.To reliably extract the RT, this method requires long pauses in the speech utterance. In this

paper we develop a novel blind RT estimation method that takes into account the interaction between the decay rates

of the room and speech. The estimator is based on a time-frequency room decay model which is related to Polacks

statistical reverberation model. A least squares method is used to continuously estimate the decay rate of the

received signal in the short-time Fourier transform (STFT) domain. The time-frequency analysis is advantageous in

two ways.Firstly, the requirement for long speech pauses is removed since it is sufficient to have any endpoints of the

signal only over the bandwidth of the frequency bin in question. Secondly, since reverberation is frequency

dependent, obtaining an estimate of the decay rate for each frequency bin can be advantageous for frequency

domain enhancements, and evaluation methods. The RT is then extracted from a property of the distribution of the

reverberant speech decay rates.

(yung.wen,p.naylor}@imperial.ac.uk) ([email protected])

Sound in lightly damped enclosures will resonate at certain frequencies, the natural frequencies. The sound

field in the room at such a resonance frequency is called a mode and the spatial distribution of the sound pressure is

called the mode shape. If losses at the walls are ignored the Helmholtz equation with the boundary conditions

imposed by the rigid walls of the room becomes an eigenvalue problem, and the mathematical solution of the

equation leads to eigenfunctions and eigenfrequencies, which are the mathematical terms for the modes and the

natural frequencies. The modes and natural frequencies cannot be determined analytically unless the room is of a

simple shape. In rooms of a more complicated geometry the solution must be found using a numerical method, such

as for example the finite element met.
mailto:[email protected]:[email protected]:[email protected]:[email protected]


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II. Layout of Design


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Dimention


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APPLIANCES


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MATERIALSFloor Materials 125 Hz 250 Hz 500 Hz1000 Hz2000 Hz4000 Hz

concrete or tile 0.01 0.01 0.015 0.02 0.02 0.02linoleum/vinyl tile on concrete 0.02 0.03 0.03 0.03 0.03 0.02

wood on joists 0.15 0.11 0.10 0.07 0.06 0.07

parquet on concrete 0.04 0.04 0.07 0.06 0.06 0.07

carpet on concrete 0.02 0.06 0.14 0.37 0.60 0.65

carpet on foam 0.08 0.24 0.57 0.69 0.71 0.73

Seating Materials 125 Hz 250 Hz 500 Hz1000 Hz2000 Hz4000 Hz

fully occupied - fabric upholstered 0.60 0.74 0.88 0.96 0.93 0.85

occupied wooden pews 0.57 0.61 0.75 0.86 0.91 0.86empty - fabric upholstered 0.49 0.66 0.80 0.88 0.82 0.70

empty metal/wood seats 0.15 0.19 0.22 0.39 0.38 0.30

Wall Materials 125 Hz 250 Hz 500 Hz1000 Hz2000 Hz4000 Hz

Brick: unglazed 0.03 0.03 0.03 0.04 0.05 0.07

Brick: unglazed & painted 0.01 0.01 0.02 0.02 0.02 0.03

Concrete block coarse 0.36 0.44 0.31 0.29 0.39 0.25

Concrete block painted 0.10 0.05 0.06 0.07 0.09 0.08

Curtain: 10 oz/sq yd fabric molleton 0.03 0.04 0.11 0.17 0.24 0.35Curtain: 14 oz/sq yd fabric molleton 0.07 0.31 0.49 0.75 0.70 0.60

Curtain: 18 oz/sq yd fabric molleton 0.14 0.35 0.55 0.72 0.70 0.65

Fiberglass: 2'' 703 no airspace 0.22 0.82 0.99 0.99 0.99 0.99

Fiberglass: spray 5'' 0.05 0.15 0.45 0.70 0.80 0.80

Fiberglass: spray 1'' 0.16 0.45 0.70 0.90 0.90 0.85

Fiberglass: 2'' rolls 0.17 0.55 0.80 0.90 0.85 0.80

Foam: Sonex 2'' 0.06 0.25 0.56 0.81 0.90 0.91

Foam: SDG 3'' 0.24 0.58 0.67 0.91 0.96 0.99

Foam: SDG 4'' 0.33 0.90 0.84 0.99 0.98 0.99

Foam: polyur. 1'' 0.13 0.22 0.68 1.00 0.92 0.97

Foam: polyur. 1/2'' 0.09 0.11 0.22 0.60 0.88 0.94

Glass: 1/4'' plate large 0.18 0.06 0.04 0.03 0.02 0.02

Glass: window 0.35 0.25 0.18 0.12 0.07 0.04

Plaster: smooth on tile/brick 0.013 0.015 0.02 0.03 0.04 0.05

Plaster: rough on lath 0.02 0.03 0.04 0.05 0.04 0.03

Marble/Tile 0.01 0.01 0.01 0.01 0.02 0.02

Sheetrock 1/2" 16" on center 0.29 0.10 0.05 0.04 0.07 0.09


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Wood: 3/8'' plywood panel 0.28 0.22 0.17 0.09 0.10 0.11

Ceiling Materials 125 Hz 250 Hz 500 Hz1000 Hz2000 Hz4000 Hz

Acoustic Tiles 0.05 0.22 0.52 0.56 0.45 0.32Acoustic Ceiling Tiles 0.70 0.66 0.72 0.92 0.88 0.75

Fiberglass: 2'' 703 no airspace 0.22 0.82 0.99 0.99 0.99 0.99

Fiberglass: spray 5" 0.05 0.15 0.45 0.70 0.80 0.80

Fiberglass: spray 1" 0.16 0.45 0.70 0.90 0.90 0.85

Fiberglass: 2'' rolls 0.17 0.55 0.80 0.90 0.85 0.80

Wood 0.15 0.11 0.10 0.07 0.06 0.07

Foam: Sonex 2'' 0.06 0.25 0.56 0.81 0.90 0.91

Foam: SDG 3'' 0.24 0.58 0.67 0.91 0.96 0.99

Foam: SDG 4'' 0.33 0.90 0.84 0.99 0.98 0.99

Foam: polyur. 1'' 0.13 0.22 0.68 1.00 0.92 0.97

Foam: polyur. 1/2'' 0.09 0.11 0.22 0.60 0.88 0.94Plaster: smooth on tile/brick 0.013 0.015 0.02 0.03 0.04 0.05

Plaster: rough on lath 0.02 0.03 0.04 0.05 0.04 0.03

Sheetrock 1/2'' 16" on center 0.29 0.10 0.05 0.04 0.07 0.09

Wood: 3/8" plywood panel 0.28 0.22 0.17 0.09 0.10 0.11

Miscellaneous Material 125 Hz 250 Hz 500 Hz1000 Hz2000 Hz4000 Hz

Water 0.008 0.008 0.013 0.015 0.020 0.025

People (adults) 0.25 0.35 0.42 0.46 0.5 0.5


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III. COMPUTATIONVOLUME OF ROOM

HIEGHT =10 ft

WIDTH = 25ft

LENGTH = 15 ft

VOLUME = WIDTH x LENGTH x HEIGTH

VOLUME = 25 x 10 x 15 = 3750ft3

SURFACE AREA OF MATERIALS

ALL INTERIOR WALLS = SAHL +SAHW SATV - SADOORALL INTERIOR WALLS = 2(10 x 23) + 2(10 x 15) - (5x6.67)( 5.8x 2.75)

ALL INTERIOR WALLS = 710.7ft2

FLOOR = (25 x 15)FLOOR = 375ft2

CEILING = (21 x 23)CEILING = 375m2

SEATS1 = 2.75x 8.33SEATS = 22.91m2

PEOPLE = 7 x/10PEOPLE = 70

TV = ( 5.8x 2.75)TV= 15.95ft2

DOOR = 5x6.67DOOR2 = 33.35ft2

SPEAKER = 3.5x1.167SPEAKER = 16.338

TABLE = 4.6 x 1.42x3TABLE = 19.596 ft


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TABLE OF MATERIALSMATERIALS

SURFACE AREA(sq.m)

ABSORPTIONCOEFFICIENT

SURFACE COEFF.(sq.ft)

Floor 375ft2 0.37 138.75

speaker 16.338 0.09 1.47042Ceiling 375ft2 0.92 345

Table 19.596ft2 0.09 1.764

Interior Walls 710.7ft2 0.07 49.749

Seating 22.91m2 0.96 2.19936

People 7 0.46 3.22

TV 15.95ft2 0.6 9.57

Door 33.35ft2 0.12 4.002

TOTAL 555.72778

RT60 = 0.049(V/A)

Where:

RT60 = Reverberation Time

V = Room volume, (ft3 or m3)

= (We used cubic meter to minimize the numbers)

A= S, S = surface area, (ft2 or m2)

= absorption coefficient of materials

= total absorption, (ft2 or m2)

RT60 = 0.049(V/A)

V = 3,750ft3

A = 555.72778ft2

RT60 = 0.049(3750/553.9787)

RT60 = 0.330 second


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IV. ConclusionIn conclusion Room acoustic parameters related to reverberance, speech clarity and sound strength have been

measured in the room. Measurement of reverberation time, speech clarity and sound strength in classroom according

to used as an indicator, with suspended absorbent ceilings and furniture, classrooms with suspended absorbent

ceilings but without furniture, classrooms without suspended absorbent ceilings and without furniture. The relations

between reverberation time and the parameters and sound strength are presented We conclude that in ordinary

classrooms with absorbent ceiling treatments there is no clear relation between reverberation time and speech

clarity parameter or reverberation time and sound strength. The reverberation time is used as a standard of the room

acoustic conditions.

On the other hand, it is also well known that rooms with almost the same reverberation time could be perceived

as acoustic different. The purposes of its rooms are normally to reduce noise levels and to create an environment

with good speech intelligibility. Often the reverberation time according to are used as an indicator of the acoustic

quality. Calculating reverberation time means that a dynamic interval of the decay curve is used for evaluation. Since

reverberation time is not evaluated until after the sound level has been reflect, the effect of early reflections is often

not included in this descriptor.

Reverberation time is therefore also denoted late or delay reverberation time. By only evaluating the

reverberation time, acoustic information that is important to the subjective experience is missed. Sound levels at

steady-state conditions and early reflections are significant for the perception of noise levels and speech clarity.

These components are not included in the reverberation time. It is therefore very important to supplement the

Reverberation time with other room acoustic descriptors interrelated to these aspects in particular.

According to the article that written in IEEE, the method was developed to estimate the reverberation time

directly from the observed reverberant speech signal. The decay rates of the energy envelope of the signal are

continuously estimated in the STFT domain using a simple least squares fitting mechanism. The distributions of the

room decay rate, the anechoic speech decay rate, and the reverberant speech decay rate were analysed. It was

found that the negative-side variance of the reverberant speech decay rate distribution is a good measure for the true


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decay rate of the room. A second order mapping function was used to find the room decay rate given the negative-

side variance of the reverberant speech decay rate distribution. The obtained decay rate is directly related to the

reverberation time of the room. Experimental results have demonstrated the beneficial use of the developed method

using simulated reverberant and real recorded speech signals.

(yung.wen, [email protected]@eng.biu.ac.il)
mailto:[email protected]:[email protected]:[email protected]:[email protected]


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Technological Institute of the Philippines

1338 Arlegui St. Quiapo, Manila

College of Engineering and Architecture

Electronics Engineering Department

Acoustics and Broadcast

Home Theater Design

Submitted by:

Gayeta, John Chester

Encio, Floredel C.

Rentoria, Daryl C.

Submitted to:

Engr.Nelor Laguna

(Instrutor)


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March 7, 2012

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Broadcast Final Design