Low-frequency interaural level differences cue source distance and signal coherence.

Evidence

As noted earlier, plane waves do not generate ILDs when their wavelengths are long compared to the size of the human head. The question then remains, why are we sensitive to ILD at low frequencies? There are at least two reasons for this. At low frequencies, the ILD is clearly a distance cue, since when the source reaches the listener, much higher ILDs are measured between the ear canals. The other use of the ILD seems to be in the perception of coherence of ear canal signals. It has been shown that humans are sensitive to very fast changes of ILD in time; the time resolution of ILD changes is of the order of a few milliseconds. If the ear canal signals are incoherent, as may happen in the case of diffuse sound, large instantaneous fluctuations in ILD are analysed (Goupell and Hartmann, 2007). — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1443

Categorization

• QUESTION: The claim that ILD serves as a near-field distance cue at low frequencies is worth verifying against head-related transfer function literature for measured near-field ILD values.
• XREF: connects to: Interaural coherence measures similarity of ear canal signals; High-frequency loss with distance provides a perceptual cue for judging sound source distance — Toole, Floyd E, Sound reproduction- the acoustics and…, 882

Broader Connections

• Interaural coherence measures similarity of ear canal signals #expands (0.75)
• High-frequency loss with distance provides a perceptual cue for judging sound source distance #expands (0.70) — Toole, Floyd E, Sound reproduction- the acoustics and…, 882