The location-dependent nature of perceptually salient features of the human head-related transfer functions.

The human head-related transfer function (HRTF) has been recorded binaurally from eight subjects using an "in-ear" recording system, for 343 stimulus locations around the head. There are a number of systematic changes in the HRTF as a function of horizontal location and elevation, on and off the median plane, that could be used as cues to sound location. To identify which components of the HRTF might provide perceptually salient cues to sound location, the HRTFs were transformed using an auditory filter model which accounts for the frequency dependence of auditory sensitivity and the frequency and level-dependent characteristics of the auditory filters. These transformations indicated a systematic variation in the frequency of the peak excitation as a function of the horizontal location of a broad band stimulus. Furthermore, there were differences in the frequency range over which elevation-dependent changes in the excitation patterns varied as a function of the vertical meridian. Interaural level differences were also estimated using the excitation patterns. The across frequency pattern of ILDs were roughly symmetrical about the interaural axis, although there were substantial differences between each ear in the magnitude of the ILDs generated for ipsilateral sounds locations.