Binaural displays based on interaural phase compensation.

Abstract

The asymmetry of many neural tuning curves to the interaural time delay (ITD) of wideband stimuli around their maximum implies that such external temporal differences are compensated by some internal phase‐delay mechanism rather than a system of axonal time delays. An internal phase delay explains why the ITD that generates maximum neural activity (best delay) is generally less than a half period of the tuning curve’s modulation (“π‐limit”). The interaural phase circle (IPD circle) and the smoothed interaural phase spectrum (SIPS) are new binaural displays, which are based on these physiological findings. The IPD‐circle displays interaural phase difference (IPD) and interaural phase coherence (IPC) of single frequency channels in a polar diagram as vector angle and magnitude, respectively. Its two‐dimensionality facilitates the study of IPD and IPC fluctuations. The SIPS shows an activation matrix of binaural coincidence detectors across their best frequencies and internal phase delays. It serves similarly to the traditional cross‐correlogram as a display of interaural temporal differences across frequency. Its computation is based on the interaural phase spectrum, which is smoothed in frequency‐dimension by the auditory filter shapes. These displays describe neural ITD tuning curves with their asymmetry, and could provide a basis for future physiologically orientated models.