Reverberation time T60 measures how long sound takes to decay a millionfold

Evidence

A measure of the reverberation time was needed; a simple number that would characterize the sound decay in any space. Sabine decided to use the time it takes for sound in the space to decay by a factor of a million (60 dB). If some source of sound has been on for a long time and the intensity in dB is measured, how long does it take to decay by a factor of a million after being abruptly cut off? This is known as the reverberation time, T60. — Eric J. Heller, Why You Hear What You Hear- An…, 2457

There are an infinite number of possible ratios that could be used. However, the most commonly used ratio is that which corresponds to a decrease in sound energy of 60 dB, or 106. This gives an equation for the 60 dB reverberation time, known as T60, which is, from Appendix 4: where T60 = the 60 dB reverberation time (in s) Equation 6. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1831

Categorization

• DEFINE: T60 defined as the time for sound energy to fall 60 dB — the field’s canonical metric.
• corroborated: 2 independent passages support this claim — Eric J. Heller, Why You Hear What You Hear- An…, 2457; David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1831