Reverberation is the persistence of sound in a room after the sound source has silenced.
The reverberation time is normally defined as the time required for the persistence of a direct sound to decay by 60 dB after the direct sound has silenced. Sometimes this dB level is indicated with a subscript and the reverberation time is given by the symbol T60. The reverberation time depends mainly on a room's volume and area and on the absorption at the walls. Generally absorption is frequency dependent and therefore the reverberation time of a room varies with frequency.
© djmw, January 7, 2011