Non-environment rooms kill the reverberant field while keeping early reflections for occupants

Evidence

However, although they are quite dead acoustically, they are not anechoic. Because for users in the room there are some reflections from the hard surfaces, there are some early reflections that make the room non-anechoic. However, sound that is emitted from the speakers is absorbed and is never able to contribute to the reverberant field. … These rooms have speakers, which are flush mounted in a reflecting wall, and a reflecting floor. The rear wall is highly absorbent, as are the side walls and ceiling. The combined effect of these treatments is that sound from the loudspeakers is absorbed instead of being reflected so that only the direct sound is heard by the listener, except for a floor reflection. However, the presence of two reflecting surfaces does support some early reflections for sources away from the speakers. This means that the acoustic environment for people in the room, although dead, is not oppressively anechoic. Proponents of this style of room say that the lack of anything but the direct sound makes it much easier to hear low-level detail in the reproduced audio and provides excellent stereo imaging. This is almost certainly due to the removal of any conflicting cues in the sound, as the floor reflection has very little effect on the stereo image. — David Howard, Jamie Angus, coustics and Psychoacoustics, 2294

Categorization

• DEFINE: Defines the ‘non-environment’ acoustic design: absorb everything from the speakers so no reverberant field forms, but keep two reflecting surfaces so the space feels dead yet audible, not oppressively anechoic.
• XREF: The insight that removing conflicting acoustic cues improves perception of low-level detail resonates with psychoacoustic masking concepts elsewhere in the book. — connects to: Very dead rooms lack a true reverberant field entirely — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1849; Small listening rooms lack diffuse reverberation and contain only early reflections — Toole, Floyd E, Sound reproduction- the acoustics and…, 477; A room can be acoustically dead yet not anechoic, with early reflections surviving. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2303

Broader Connections

• A room can be acoustically dead yet not anechoic, with early reflections surviving. #expands (0.95) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2303
• Small listening rooms lack diffuse reverberation and contain only early reflections #exemplifies (0.90) — Toole, Floyd E, Sound reproduction- the acoustics and…, 477
• Very dead rooms lack a true reverberant field entirely #qualifies (0.85) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1849