ABSTRACT
The sound pressures generated at the eardrums measure the response of a complex acoustical antenna system that couples the ears to the sound field. This system includes the head and external ears. The variations in response with source direction and frequency provide the physical basis for sound localization. Treating the head as a sphere and the ears as simple detectors provides useful values of interaural time difference but overlooks the effects of pinna diffraction and concha wave motion, which are significant at high frequencies. These effects have been studied in real human ears, replicas, and geometrical models using special sound sources close to the ear. Each human ear has distinctive patterns of response while sharing major features with other ears. These common characteristics are linked to the normal modes of the concha and can be reproduced in mode-matched physical models. When sounds are presented through earphones, the free-field characteristics of the ear are replaced by very different characteristics that are dependent on complex and unreliable interactions between the individ ual earphone and the individual ear. These interactions, which vary greatly with the class of earphone, pose challenges where there is a need to reproduce the subtleties of spatial hearing.
