measured reverberation time

AUDITORUIM/THEATER PETA-PHINMA Theater

MEASURED REVERBERATION TIME

The proponents used the application ClapIR in measuring the reverberation time inside the PETA-PHINMA Theater. With a corresponding distance per clap, the reverberation time is measured. The first distance is from 5 feet from the sound source or the clap. And the distance between the first point of measurement to the second point is 15 feet. The proponents only measured a total of 4 claps and get the total average of reverberation time measured to be compared to the computed reverberation time.

Measuring the reverberation time using the ClapIR application

Distance from the sound source (clap) : 5 feet

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Distance from the sound source (clap): 20 feet

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As the proponents finish the measurement of reverberation time in a particular distance, the proponents analyze the data and come up with the table below. The table consists of the claps from the distances inside the PETA-PHINMA Theater.

Distance (feet)

Reverberation Time

(seconds)1st Clap 5 feet 1.53 seconds

2nd Clap 20 feet 1.49 seconds

3rd Clap 35 feet 1.22 seconds

4th Clap 50 feet 1.15 seconds

Measured Reverberation Time Table

The proponents get the average reverberation time to be used for the comparison of the measured and the computed value.

Average RT60 (Measured )=RT1+RT2+RT3+RT 4

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Average RT60 (Measured )=1.53+1.49+1.22+1.15

4=1.3475 seconds

REVERBERATION TIME COMPUTATION

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Given:

Volume (empty) = 2426.841

Volume (full) = 2092.5

Surface Area (S) = 1160.42

Absorption Coefficient Full (α) = 0.267

Absorption Coefficient Empty (α) = 0.287

r ( orchestra ) = 5

Computation for Ideal RT60:

Using the Stephen and Bate Equation

Computation for Ideal RT60( Empty):

Ideal RT60 (empty )=r (0.012 3√V empty +.1070 ) Ideal RT60 (empty )=5 (0.012 3√2426.841+.1070 )Ideal RT60 (empty )=1.34786 secs

Computation for Ideal RT60( Full):

Ideal RT60 (empty )=r (0.012 3√V Full+.1070 ) Ideal RT60 (full )=5 (0.012 3√2092.5+.1070 )

Ideal RT60 (full )=1.30243 secs

Computation for Computed RT 60:

Using the Norris - Eyring Equation

Computation for Computed RT 60(Empty):

RT60 (Empty)=0.161V Empty

−S ln (1−α Empty)

RT60 ( empty )=0.161 (2486.841 )

−(1160.42 ) ln (1−0.287 )

RT60 ( empty )=1.2754 secs

Computation for Computed RT 60(Full ):

RT60 (Full)=0.161V Full

−S ln (1−αFull)

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RT60 ( full)=0.161 (2092.5 )

−(1160.42 ) ln (1−0.267 )

RT60 ( full)=0.9347 secs

PERCENTAGE DIFFERENCE

Given:

Computed RT 60( empty )=1.2754 secs

Computed RT 60( full )=0.9347 secs

Measured RT60 (empty )=1.3475 secs

Computation for Empty:

%Diff =Measured RT60 – Computed RT60 (Empty)

Measured RT 60

×100

%Diff =1.3475 secs –1.2754 secs1.3475 secs

×100

%Diff =5.3506%

Computation for Full:

%Diff =Measured RT60 – Computed RT60 (Full)

Measured RT60×100

%Diff =1.3475 secs –0.9347 secs1.3475 secs

×100

%Diff =30.6345%

COMPARISON OF RT60 COMPUTED TO THE MEASURED VALUE OF RT60

The proponents measure the Reverberation Time inside the PETA-PHINMA Theater. And for

the computation of the empty room the proponents sum up all the value of the absorption

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coefficient of the flooring, ceiling, walls and other miscellaneous material and divides it by the total

number of materials, and the proponents get the value of alpha which is equal to 0.237 for empty

room and for full capacity the value of alpha is 0.267, that is why in solving the RT60 the

proponents used the formula of Norris-Eyering because the value of the alpha that the proponents

get is greater than 0.2 which is the requirement for Norris-Eyering equation.

As the proponents gathered the data, the proponents computed the value for full and empty

room. By solving simultaneously the value of the RT60 of a full room is 0.9347 seconds, which is

slightly close to the average measured Reverberation Time of 1.3475 seconds which gives us

30.6345% by using the percentage difference. Lastly, for Empty room the value of RT60 is

approximately 1.34786 seconds which is close to the average measured Reverberation Time of

1.3475 seconds which gives us 5.3506% error.

The proponents compared the measured value to the ideal value of the Reverberation time for

empty room which is 1.34786 seconds using the Stephen and Bate formula. And for the full

capacity the ideal reverberation time is 1.3024. The measured value is somewhat close to the ideal

reverberation time. And therefore the proponents conclude that the design of the room is for

acoustic purposes.

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measured reverberation time

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