Ideal reverberation is a smooth exponential decay whose rate depends on context.
Evidence
Equation 6.16 gives us the time between surface interactions, and at each of these interactions, α is the proportion of the energy absorbed, where α is the average absorption coefficient discussed earlier. If α of the energy absorbed at the surface, then (1 − α) is the proportion of the energy reflected back to interact with further surfaces. At each surface a further proportion, α, of energy will be removed, so the proportion of the original sound energy that is reflected will reduce exponentially. The combination of the time between reflections and the exponential decay of the sound energy, through progressive interactions with the surfaces of the room, can be used to derive an expression for the length of time that it would take for the initial energy to decay by a given ratio. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1830 (
#corroborates, via linked claim)
W. C. Sabine, the acoustician, has defined reverberation time technically. It is the time that elapses from the instant a sound source is switched off until its energy decays to one millionth of its original strength (a drop of 60 decibels). As far as the ear is concerned, it is the time it takes for a sound to melt and be lost in the ambient noise. Echo differs from reverberation in that it is a repetition or partial repetition of a sound, due to reflection off a distant surface. Reverberation is also reflected sound but no separate repetitions of the original are distinguishable. — Schafer, Murray R, The Soundscape- Our Sonic Environment…, 446 (
#expands, via linked claim)
Categorization
- XREF: connects to: A single slope measurement of dB decay directly yields the reverberation time; Reverberation time is defined as a 60-decibel energy decay — Schafer, Murray R, The Soundscape- Our Sonic Environment…, 446; Room modes produce multiple decay times instead of a single exponential reverberation — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1996 (+7 more)
Broader Connections
- Room sound energy decays exponentially through repeated surface absorptions
#corroborates(0.90) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1830 - Reverberation time is defined as a 60-decibel energy decay
#expands(0.85) — Schafer, Murray R, The Soundscape- Our Sonic Environment…, 446 - Sabine experimentally verified exponential sound decay in a reverberant room
#corroborates(0.85) - Room modes produce multiple decay times instead of a single exponential reverberation
#qualifies(0.80) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1996 - Absorption at each reflection governs how fast reverberation decays
#expands(0.80) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1743 - Room sound homogeneous decay holds for typical rooms but can be engineered away
#qualifies(0.80) - Reverberation time depends on both surface absorption and time between reflections
#expands(0.80) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1824 - Reverberation time depends on room volume and surface area, not absorption alone.
#expands(0.75) — Eric J. Heller, Why You Hear What You Hear- An…, 2476 - Room absorption determines the steady-state level of reverberant sound
#expands(0.75) — David Howard, Jamie Angus, coustics and Psychoacoustics, 1781