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Reverberation Time in "Dead" Rooms

With the advent of radio and sound-picture studios, it was recognized that Sabine's formula applied only to "live" as distinguished from "dead" rooms. A live room may be considered as one having a reverberation time of more than one second, and a dead room as one having a reverberation time of less than one second.

The reverberation time in any room is given9 by the expression

in which T is the reverberation time in seconds, k = 0.05 (approximately, see reference 12) for a diffuse condition of the sound energy, V is the volume of the room in cubic feet, S is the total room surface in square feet, and αa is the average absorbing coefficient. This average coefficient is found by the expression

That is, αa is found by adding the products of each different surface area and its corresponding absorption coefficient, and dividing this sum by the total room surface in square feet.

A simple correction makes equation 4 applicable to "dead" rooms. If 0.027V/S is subtracted from the reverberation time as given by equation 4, the corrected reverberation time will be substantially as found by equation 5. In this correction, V and S are as previously considered.10



Last Update: 2011-05-30