The time it takes for the reverberation in a room to decrease by 60dB. Hard surfaces and the size of the room contribute to the RT60.

The standard method for specifying reverberation time, RT60 is the amount of time it takes for the reverberant energy in an enclosed space to drop by 60 dB from its initial, steady-state value after the original sound has ceased. Large rooms with hard, highly reflective surfaces (like cathedrals) have long reverberation times, while smaller rooms with absorptive surfaces have short reverberation times. Here is a diagram that gives preferred RT60 values for various applications. Return to

The time required for sound to drop to - 60 dB in level once the source of sound has been stopped; the -60 dB is below that of the measured level in the steady state or while the sound system was on and after any initial transients or fluctuations settled.