Room sound energy decays exponentially through repeated surface absorptions
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
Categorization
- XREF: Connects to the mean free path concept and the general physics of exponential decay, familiar from acoustics theory in earlier chapters of this book. — connects to: Room sound homogeneous decay holds for typical rooms but can be engineered away; Sabine experimentally verified exponential sound decay in a reverberant room; Low absorber rooms raise overall sound level because reverberant energy persists longer — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1756 (+11 more)
- corroborated: 3 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1830
Broader Connections
- Room modes produce multiple decay times instead of a single exponential reverberation
#qualifies(0.85) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1996 - Total surface area can outweigh absorption efficiency in controlling room reverberation
#expands(0.80) — David Howard, Jamie Angus, coustics and Psychoacoustics, 1929 - Physical sound absorption can be strong enough to measurably alter room reverberation
#expands(0.78)