What is reverberation time ?

Work on room acoustics was pioneered by Wallace Clement Sabine 1868-
1919 (see his Collected Papers on Acoustics, 1922).
The reverberation time, T, is defined as the time taken for sound
energy to decay in a room by a factor of one million (ie by 60 dB). It
is dependent on the room volume and its total absorption.

In metric units

0.161 x room Volume
T = ———————————————-
sum of Surface areas x absorption coefficients