True diffuse sound fields cannot form in small absorptive listening rooms

Evidence

Calculation of the Schroeder frequency assumes meaningful reverberation times, a strongly diffuse sound field and a volume unimpeded by large objects (furniture and people are large objects in small rooms). Small listening rooms and recording control rooms are too absorptive to have a meaningful diffuse sound field and a reverberation time—a reflection decay time would be a better description at middle and high frequencies and resonance ringing time at low frequencies. — Toole, Floyd E, Sound reproduction- the acoustics and…, 477 (#corroborates, 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 (#expands, via linked claim)

Categorization

• XREF: connects to: The Sabine formula assumes diffuse sound that real rectangular rooms rarely produce; Rectangular rooms fail to randomize sound directions, violating Sabine theory; Envelopment cues below about 80 Hz cannot be reproduced in small listening rooms (+15 more)

Broader Connections

• Real listening rooms produce semi-reflective fields, not free or diffuse fields #corroborates (0.95)
• Small listening rooms lack diffuse reverberation and contain only early reflections #corroborates (0.92) — Toole, Floyd E, Sound reproduction- the acoustics and…, 477
• The diffuse field assumption underpins room acoustics predictions but fails at low frequencies #qualifies (0.85)
• Statistical acoustics and classical critical distance do not apply in small rooms #expands (0.85) — Toole, Floyd E, Sound reproduction- the acoustics and…, 1312
• Non-environment rooms suppress all but direct sound for clearer audio detail and imaging #exemplifies (0.82)
• Smaller rooms produce louder reverberant fields but shorter reverberation times #qualifies (0.80) — David Howard, Jamie Angus, coustics and Psychoacoustics, 1806
• Distributing absorption in small random amounts around a room improves sound diffusion #complicates (0.75)