At high frequencies rooms act as irregular interference fields rather than standing-wave patterns

Evidence

The room curves displayed in Chapter 5 show that the right combination of anechoic measurements can closely anticipate events in typical rooms at middle and high frequencies, but at low frequencies the curves are lumpy and irregular. The acoustical explanation is the dominance of relatively isolated room modes and associated standing waves at low frequencies, and of a complex collection of overlapping modes and reflected sounds at high frequencies. As a result, as frequency increases it becomes progressively less useful to think about regular patterns of standing waves in rooms, but rather to think in terms of irregular patterns of constructive and destructive acoustical interference caused by numerous reflections traveling in many directions. — , Toole, Floyd E - Sound reproduction-…, 626 (#corroborates, via linked claim)

If the anechoic loudspeaker data do not reveal evidence of resonances, fluctuations in steady-state room curves are almost certainly attributable to acoustical interference. It is highly improbable that the propagation path from the loudspeaker to the microphone/listener contains a potent acoustical resonance mechanism above the transition frequency. — , Toole, Floyd E - Sound reproduction-…, 412 (#expands, via linked claim)

Even with seat counts that range through 6, 24, 60, 114, 161, 211 and 516, there is no obvious pattern of change in steady-state room curves above about 400 Hz except the small difference in high-frequency air attenuation in the direct sound related to listening distance. Air attenuation can be calculated for any seat in any venue (see Section 12.3.6). All curves in all venues reflect expectations from anechoic data except at low frequencies where room resonances and boundary interactions dominate. Only at low frequencies are room curves revealing new information, and a basis for equalization or other forms of room mode control. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1338 (#corroborates, via linked claim)

Categorization

• XREF: connects to: Room resonances shift from isolated to overlapping at the Schroeder frequency; Interference pattern of correlated sources varies with both listener position and frequency — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 241; Room acoustics shift from standing waves to irregular interference as frequency rises — , Toole, Floyd E - Sound reproduction-…, 626 (+9 more)

Broader Connections

• Room acoustics shift from standing waves to irregular interference as frequency rises #corroborates (1.00) — , Toole, Floyd E - Sound reproduction-…, 626
• Above the transition frequency room-curve wiggles are interference, not resonances #expands (0.92) — , Toole, Floyd E - Sound reproduction-…, 412
• Room size does not alter steady-state curves above 400 Hz #corroborates (0.80) — Toole, Floyd E, Sound reproduction- the acoustics and…, 1338
• Larger rooms exhibit lower critical frequencies because volume scales with size #expands (0.75) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2037
• Room mode coupling depends on source and listener positions, not frequency #contradicts (0.72)