Limited human spatial resolution allows plausible upmix from fewer source channels

Evidence

The purpose of these extra channels is to improve the surround-sound experience for the listener so that they have more consistent localization all the way around themselves. In addition, some arrangements can be used to give an illusion of source height, which can give the listener a more realistic sense of the environment the reproduced sound is in. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2227 (#corroborates, via linked claim)

Categorization

• XREF: connects to: Horizontal-plane localization is mature while elevation reproduction is newly addressed; Extra surround channels mainly aim at consistent localization and height illusion — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2227; Adding rear channels to stereo does not improve spatial diffusion — , Toole, Floyd E - Sound reproduction-…, 1670 (+2 more)

Broader Connections

• Spatial audio systems create illusions of direction and space rather than reproducing them exactly #expands (0.82)
• Extra surround channels mainly aim at consistent localization and height illusion #corroborates (0.78) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2227
• Spatial envelopment requires uncorrelated ear signals, not a diffuse sound field #complicates (0.75)
• Adding rear channels to stereo does not improve spatial diffusion #contradicts (0.74) — , Toole, Floyd E - Sound reproduction-…, 1670