Room acoustics shift from standing waves to irregular interference as frequency rises

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

Categorization

• DEFINE: Explains the qualitative crossover from low-frequency modal behavior to high-frequency diffuse interference in rooms.
• XREF: connects to: Room resonances shift from isolated to overlapping at the Schroeder frequency; Geometric acoustics fails on diffraction at low frequencies in complex rooms — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 303; Interference pattern of correlated sources varies with both listener position and frequency — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 241 (+8 more)

Broader Connections

• Room mode density rising smoothly with frequency signals good acoustics #corroborates (0.85) — Eric J. Heller, Why You Hear What You Hear- An…, 2435
• Diffuse surfaces make room acoustics degrade gradually away from the sweet spot #corroborates (0.75)