Decomposition of the Hrtf from a Sphere with Neck and Hair

Sphere scattering models are commonly used with binaural synthesis as they provide a convenient approximation of the acoustic characteristics of the human head. However these models suffer from being an over simplification of human geometry, and if used in isolation provide ambiguous source location cues. Such models also over exemplify the lobe of increased pressure (bright spot) that occurs at the rear of the sphere due to symmetrically diffracted waves arriving in phase. This paper uses decomposition to examine how the addition of a cylindrical neck and hemispherical hair covering alters the azimuthal head-related transfer function (HRTF) from a rigid sphere (up to 5 kHz). Neither anthropometric feature provides a major perturbation of the sphere HRTF. The neck produces a reduction in the bright spot magnitude in the order of 2-4 dB. The hair produces asymmetrical changes to the HRTF for ipsilateral angles in the order of 1-2 dB. Additional asymmetric reductions in the order of 2-4 dB are seen for contralateral angles when the source is near the interaural axis. [