The effect of hair on auditory localization cues.

Previous empirical and analytical investigations into human sound localization have illustrated that the head-related transfer function (HRTF) and interaural cues are affected by the acoustic material properties of the head. This study utilizes a recent analytical treatment of the sphere scattering problem (which accounts for a hemispherically divided surface boundary) to investigate the contribution of hair to the auditory cues below 5 kHz. The hair is modeled using a locally reactive equivalent impedance parameter, and cue changes are discussed for several cases of measured hair impedance. The hair is shown to produce asymmetric perturbations to the HRTF and the interaural time and level differences. The changes in the azimuth plane are explicated via analytical examination of the surface pressure variations with source angle. Experimental HRTFs obtained using a sphere with and without a hemispherical covering of synthetic hair show a good agreement with analytical results. Additional experimental and analytical investigations illustrate that the relative contribution of the hair remains robust, regardless of the placement of the pinnas, or inclusion of a cylindrical neck.