Rectangular rooms fail to randomize sound directions, violating Sabine theory

Evidence

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 (#corroborates, via linked claim)

Equation A5.3 is also known as the “Millington–Sette equation.” Although Equation A5.3 can be used irrespective of the absorption level it is still more complicated than the Sabine equation, and if the absorption coeffi­ cient is less than 0.3 it can be approximated very effectively by it, as dis­ cussed previously. Thus in many contexts the Sabine equation, Equation A5.1, is preferred. — David Howard, Jamie Angus, coustics and Psychoacoustics, 2848 (#qualifies, via linked claim)

This brief analysis is a good example of just how predictable modal events are in a known rectangular room when the woofer and microphone locations are well defined. This underlines the huge advantage of rectangular rooms—the low-frequency sound fields can be substantially predicted in advance and measurements interpreted after the fact. Knowing which modes cause problems allow solutions to be focused. Obviously, only high-resolution measurements allow for this depth of analysis. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1635 (#qualifies, via linked claim)

Categorization

• XREF: connects to: The Sabine formula assumes diffuse sound that real rectangular rooms rarely produce; Statistical acoustics and classical critical distance do not apply in small rooms — Toole, Floyd E, Sound reproduction- the acoustics and…, 1312; The diffuse field assumption underpins room acoustics predictions but fails at low frequencies (+5 more)

Broader Connections

• Statistical acoustics and classical critical distance do not apply in small rooms #corroborates (0.85) — Toole, Floyd E, Sound reproduction- the acoustics and…, 1312
• The Sabine equation works well when absorption coefficients stay under 0.3 #qualifies (0.85) — David Howard, Jamie Angus, coustics and Psychoacoustics, 2848
• The diffuse field assumption underpins room acoustics predictions but fails at low frequencies #corroborates (0.80)
• Rectangular rooms allow predicting low-frequency modal behavior in advance #qualifies (0.80) — Toole, Floyd E, Sound reproduction- the acoustics and…, 1635
• True diffuse sound fields cannot form in small absorptive listening rooms #corroborates (0.75)