High-frequency tones produce ambiguous azimuthal localization due to phase wrapping.

Evidence

Because this tone cycles many times over 630 µs, there are multiple sound source locations that result in the same IPD. For a 5000-Hz tone presented to the left ear, the IPD is equal to 1134° [(630 µs/200 µs) * 360°], but this value is equivalent to 774°, 414°, and 54°. In this case, the sound could be originating from one of four azimuthal locations. In this way, phase differences across the ears provide ambiguous information about location on the horizontal plane. As a prime example, consider that when a tone of 1587 Hz (which has a period of 630 µs) is presented to the left ear, the IPD is 0°, (630 µs/630 µs * 360° = 0°). In this case, one would not be able differentiate whether the sound is presented to the left side or to the front of the body. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 1467

Categorization

• DEFINE: Concretely demonstrates IPD ambiguity via phase wrapping at frequencies above the head-shadow ITD limit.
• XREF: connects to: Phase-based localization sensing has a hard frequency ceiling near 1.6 kHz — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1430; Phase delays beyond 180 degrees make direction judgments ambiguous — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 720