The reverberation time is the time, measured in seconds, that passes from when a sound source is interrupted until the sound dies out. It is the character and acoustic properties of the surrounding surfaces that determine how sound waves behave and propagate.

When a sound wave hits an obstruction, it is reverberated. If the surface is hard and even, the sound wave will be reverberated directly, while a soft and uneven surface will absorb part of the sound waves and delay or muffle the reverberation.

 

Normally, a long reverberation time is undesirable as the echo effect of the first sound waves mixes with the subsequent sound waves. The result is a noisy and resonant acoustic image in which it is difficult to distinguish individual sounds.

Long reverberation time		Short reverberation time

With a short reverberation time, the acoustic image becomes more precise and sharp, and the speech intelligibility is increased significantly. 

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