A speaker near hard surfaces produces phantom image sources that color its sound

Evidence

It is a clearly audible effect. Plenge (1987) explains it, as done here, and goes on to relate it to some theories of timbre perception, pointing out along the way that most listeners do not sit still, and are obviously not bothered by the consequent changes in sound image location and timbre. However, dedicated audiophiles and recording engineers who gravitate to the stereo seat are exceptions. Augspurger (1990) describes how easy it is to hear the effect using 1/3-octave bands of pink noise, observing a “distinct null at 2 kHz” (p. 177). Pulkki (2001) confirmed that the comb filter was the dominant audible coloration in anechoic listening to amplitude-panned virtual images, but that it was lessened by room reflections. Listeners in experiments by Choisel and Wickelmaier (2007) reported a reduction in brightness when a mono center loudspeaker was replaced by a stereo phantom image (their figure 4). Listeners in the Shirley et al. (2007) experiments not only heard the dip seen in Figure 7.2e but demonstrated that it had a significant negative effect on speech intelligibility. This is hardly the epitome of sound reproduction technology. — , Toole, Floyd E - Sound reproduction-…, 673 (#corroborates, via linked claim)

Categorization

• XREF: connects to: Ground reflection colors all outdoor speech and creates comb-filter pitch; A single sound source near a reflecting surface creates interference via an image source — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 366; Phantom center image sound quality is inherently compromised even in the sweet spot (+7 more)

Broader Connections

• Room boundaries alter loudspeaker output through reflected image sources #expands (0.95)
• The stereo phantom center image suffers an audible 2kHz timbre dip affecting speech intelligibility #corroborates (0.85) — , Toole, Floyd E - Sound reproduction-…, 673
• Multichannel spatial information masks loudspeaker coloration in playback #contradicts (0.80)
• Nearby reflecting surfaces constructively pile up wave reflections to amplify sound #expands (0.80)
• Room echoes sculpt sharp resonant peaks into a sound’s spectrum #expands (0.75)
• Moving sources make reflected-sound comb-filtering audible as pitch rather than mere colouration #expands (0.75)