Low-frequency room resonances dominate how loudspeaker placement affects perceived quality.

Evidence

In retrospect, we now know that room resonances at low frequencies account for about 30% of overall evaluations of sound quality, so adhering to the new standard is no assurance of obtaining “standardized” subjective data. Room modes will be different for different IEC rooms, so some form of control or normalization is required below about 300 to 500 Hz to evaluate what is happening at higher frequencies. — Toole, Floyd E, Sound reproduction- the acoustics and…, 146

Earlier tests had confirmed the fact that the location of a loudspeaker in a room affects its sound quality rating, and that low-frequency room resonances were a large part of the effect (Olive et al., 1992, 1994). — Toole, Floyd E, Sound reproduction- the acoustics and…, 523

Categorization

• QUESTION: What exactly is the 30% figure measuring — variance contribution, listener weighting, or something else? Worth chasing the original study.
• XREF: Directly relevant to the reader’s audio/coding work: room modes dominate quality assessment below 300-500 Hz.
• corroborated: 2 independent passages support this claim — Toole, Floyd E, Sound reproduction- the acoustics and…, 146; Toole, Floyd E, Sound reproduction- the acoustics and…, 523