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Matt, Mechanical Engineer
Category: Engineering
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Experience:  BEng hons Mech engineering, in auto industry 22 years
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How did Wallace Sabine find 0.161 as the constant value for

Customer Question

How did Wallace Sabine find 0.161 as the constant value for calculating reverb time in a room?
Submitted: 3 years ago.
Category: Engineering
Expert:  Patience replied 3 years ago.

Hello- Thanks for your question. Please read the answer below and then give a good rating. Then if you have any further questions, I would be happy to help at no extra charge. Good luck in your studies, Patience P.

Wallace Sabine was an assistant professor of physics at Harvard in 1898.At that time, a lecture hall at the university called Fogg Hall had such a bad echo that it couldn’t be used for lecture classes.

Sabine was asked to determine what factors were controlling the length of time it took for the sound to die away in the hall and that were contributing to the echo effect. He decided to use a 512 Hz note as a reference point, and then he timed how long it took the sound to die away completely.

After making thousands of measurements in various buildings at Harvard, he discovered something that he called "reverberation time."This phenomena was related to the volume of the room and the absorbency of the materials on the room’s surfaces.

Sabine started making his calculations about this with several assumptions. He assumed that the sound field in a room was perfectly diffuse; absorption was evenly distributed throughout the room; and that the reverberation time obtained for a 512 Hz tone would be representative of all frequencies in the room.

He used his assumptions to come up with an equation for calculating the reverberation time of a room, and he published his findings in October 1898.

Sabine’s equation stated that:

The reverberation time (RT) in seconds is proportional to the ratio of the room volume V (in cubic meters) and the total absorption A of all the surfaces in the room. The constant of proportionality is based on the speed of sound, but for the purposes of rooms at normal atmospheric pressure and temperature (20°C), 0.161 is an acceptable value.

Customer: replied 3 years ago.
Thank you for your answer. Unfortunately it doesn't address the key point of my question. How did he arrive at 0.161 as the constant value? Where did that figure come from? Is it a coincidence that 0.161 is a sixth?
Expert:  Matt replied 3 years ago.

another expert here

the 0.161 constant was arrived at by empircial / experimental measurement, as Patience's answer stated' After making thousands of measurements'

so this constant would have been adjusted and tweaked many times to provide a 'best fit' with his equation

this is common practice in scientific expiriments

please can you rate Patiences answer as she did the work on this one