Physical sound absorption can be strong enough to measurably alter room reverberation

Evidence

What is the 60 dB reverberation time (T60) of a living room as a function of frequency whose surface area is 75 m2 and whose volume is 42 m3? The floor is carpet on concrete, the ceiling is plaster on lath, and both have an area of 16.8 m2. There are 6 m2 of windows and the rest of the surfaces are painted plaster on brick; ignore the effect of the door. Using the data in Table 6.1, set up a spreadsheet or table, as shown in Table 6.2, and calculate the equivalent open window area for each surface as a function of frequency. Having done that add up the individual surface contributions for each frequency band and apply Equation 6.20 to the result in order to calculate the reverberation time. — David Howard, Jamie Angus, coustics and Psychoacoustics, 1929 (#qualifies, via linked claim)

Second, because in the steady state the reverberant sound at any time instant is the sum of all the energy in the reverberation tail, the overall sound level is increased by reverberation. The level of the reverberation will depend on how fast the sound is absorbed in the room. A low level of absorption will result in sound that stays around in the room for longer and so will give a higher level of reverberant field. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1756 (#expands, via linked claim)

If a steady tone, such as an organ note, is played in the space then after a period of time the reverberant sound will reach a constant level because at that point the sound power input balances the power lost by absorption in the space. This means that the steady-state level will be higher in rooms that have a small amount of absorption, compared with rooms that have a lot of absorption. — David Howard, Jamie Angus, coustics and Psychoacoustics, 1781 (#expands, via linked claim)

Categorization

• XREF: connects to: Occupied audiences absorb up to 90 percent of incident sound in a hall; Total surface area can outweigh absorption efficiency in controlling room reverberation — David Howard, Jamie Angus, coustics and Psychoacoustics, 1929; Room absorption determines the steady-state level of reverberant sound — David Howard, Jamie Angus, coustics and Psychoacoustics, 1781 (+12 more)

Broader Connections

• Total surface area can outweigh absorption efficiency in controlling room reverberation #qualifies (0.75) — David Howard, Jamie Angus, coustics and Psychoacoustics, 1929
• Low absorber rooms raise overall sound level because reverberant energy persists longer #expands (0.72) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1756
• Room absorption determines the steady-state level of reverberant sound #expands (0.70) — David Howard, Jamie Angus, coustics and Psychoacoustics, 1781