– Acoustic decay, or decay time, describes how much time is required for a sound to decay after it stops. Think of a cathedral when the music / singing stops, there is a certain amount of time for the sound to decay to the point where you no longer hear it.
– Typically, this is known as the RT60 time (or how long it takes for the sound to decay by 60 decibels), but in practice, that’s a huge difference in loudness – an RT10 or RT20 time probably makes more sense. In any case, RT60, RT20, what have you is a method typically used in large spaces (cathedrals, concert halls etc).
– It’s of little importance in a space like a home theater, because the decay times are so short that such a measurement doesn’t convey any real useful information. For listening rooms / media rooms, other methods are better, and we can discuss these with you.