Interaural timing alone cannot explain our sound localization ability

Evidence

Sound arrives first at the ear closest to the source. We detect this small arrival time difference and use it to help determine the direction of the source. However, our ability to localize sound is much better than this interaural time delay can account for. A source can be equidistant to both ears anywhere in a medial plane, extending from the horizon to the zenith overhead, all the way to directly behind the listener, but we can accurately estimate the height and the distance of the source in this plane. This is true, though to less precision, even with one deaf ear (although bone conduction of sound, down by more than 40 dB, may still play a role). It is clear that something else besides time of arrival differences at the two ears is supplying information about location of the source. — Eric J. Heller, Why You Hear What You Hear- An…, 1929

Categorization

• QUESTION: What exactly is the mechanism supplying the extra localization information? This sets up the pinna-reflection explanation that follows, and invites deeper investigation of mono-aurally perceived elevation.
• XREF: connects to: The ear’s 1-2 ms time resolution makes monaural temporal cues unusable for localization. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1450; Front and back sound localization requires other mechanisms than ITD — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 717