Diffusing surfaces may not reduce perceived reflection loudness as expected

Evidence

Angus (1997, 1999) compared large single, lateral reflections from a side wall with diffuse (i.e. multiple small) reflections from the same surface covered with scattering elements. There were no subjective tests, but mathematical simulations showed some counter-intuitive results, namely that although the amplitudes of individual reflections were attenuated (as seen in an ETC), the variations in frequency responses measured at the listening position were not necessarily reduced. If the Cremer and Müller perceptual-summation effect is incorporated, the multiple smaller reflections seen in the ETC may end up being perceived as louder than anticipated. It is suggested, however, that a diffuse reflecting surface may make listening position less critical. — Toole, Floyd E, Sound reproduction- the acoustics and…, 655

Categorization

• QUESTION: The Cremer and Müller perceptual-summation effect is referenced but not explained here — worth chasing what it actually is.
• corroborated: 2 independent passages support this claim — Toole, Floyd E, Sound reproduction- the acoustics and…, 655
• XREF: connects to: Early reflections boost perceived loudness while loud late reverberation degrades intelligibility — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 273; Diffusers mainly attenuate specific reflections rather than create diffuse fields — Toole, Floyd E, Sound reproduction- the acoustics and…, 1257; Floor reflections are perceptually benign and removing them sounds unnatural. (+3 more)

Broader Connections

• Early reflections boost perceived loudness while loud late reverberation degrades intelligibility #complicates (0.80) — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 273