### Audio Decay Time (T60)

In audio, a decay by (one time-constant) is not enough to become inaudible, unless the starting amplitude was extremely small. In architectural acoustics (which includes the design of concert halls [4]), a more commonly used measure of decay is '' (or T60), which is defined as the time to decay by dB.4.7That is, is obtained by solving the equation

Using the definition of the exponential , we find

Thus, is about seven time constants. See where is marked on Fig.4.7 compared with .

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