No reverberation-time formula has universal applicability across rooms

Evidence

If reflecting off walls and the like causes the sound energy decay, one has only to determine how often sound hits something in a room, and then properly weigh how much sound is lost. Sound in a small room encounters more reflections per second and therefore will die out faster than in a large room made of the same materials. Heavy curtains and pillows absorb far more sound than brick walls do. A derivation of the Sabine formula for the reverberation time T60, defined as the time it takes for sound to die down in energy by a factor of a million (which is about when a loud sound fades out to inaudibility) is given in box 27.2. — Eric J. Heller, Why You Hear What You Hear- An…, 2476 (#corroborates, via linked claim)

The decay of sound energy in the room is no longer a single exponential decay with a time constant proportional to the average absorption in the room. Instead, there are several decay times. The shortest one tends to be due to the diffuse sound field, whereas the longer ones tend to be due to the resonant modes in the room. This results in excess energy at those frequencies with the attendant degradation of the sound in the room. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1996 (#complicates, via linked claim)

The sound field in small listening rooms is not diffuse, statistical acoustics do not apply, and there is no critical distance, as classically defined. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1312 (#complicates, via linked claim)

Categorization

• XREF: 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; Identical reverberation times can mask drastically different room sizes and acoustics (+10 more)

Broader Connections

• Reverberation time depends on room volume and surface area, not absorption alone. #corroborates (0.82) — Eric J. Heller, Why You Hear What You Hear- An…, 2476
• Room modes produce multiple decay times instead of a single exponential reverberation #complicates (0.78) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1996
• Smaller rooms produce louder reverberant fields but shorter reverberation times #corroborates (0.75) — David Howard, Jamie Angus, coustics and Psychoacoustics, 1806
• Statistical acoustics and classical critical distance do not apply in small rooms #complicates (0.75) — Toole, Floyd E, Sound reproduction- the acoustics and…, 1312