LOCALIZATION USING NONINDIVIDUALIZED HEAD-RELATED TRANSFER-FUNCTIONS

A recent development in human-computer interfaces is the virtual acous tic display, a device that synthesizes three-dimensional, spatial audi tory information over headphones using digital filters constructed fro m head-related transfer functions (HRTFs). The utility of such a displ ay depends on the accuracy with which listeners can localize virtual s ound sources. A previous study [F. L. Wightman and D. J. Kistler, J. A coust. Soc. Am. 85, 868-878 (1989)] observed accurate localization by listeners for free-field sources and for virtual sources generated fro m the subjects' own HRTFs. In practice, measurement of the HRTFs of ea ch potential user of a spatial auditory display may not be feasible. T hus, a critical research question is whether listeners can obtain adeq uate localization cues from stimuli based on nonindividualized transfo rms. Here, inexperienced listeners judged the apparent direction (azim uth and elevation) of wideband noisebursts presented in the free-field or over headphones; headphone stimuli were synthesized using HRTFs fr om a representative subject of Wightman and Kistler. When confusions w ere resolved, localization of virtual sources was quite accurate and c omparable to the free-field sources for 12 of the 16 subjects. Of the remaining subjects, 2 showed poor elevation accuracy in both stimulus conditions, and 2 showed degraded elevation accuracy with virtual sour ces. Many of the listeners also showed high rates of front-back and up -down confusions that increased significantly for virtual sources comp ared to the free-field stimuli. These data suggest that while the inte raural cues to horizontal location are robust, the spectral cues consi dered important for resolving location along a particular cone-of-conf usion are distorted by a synthesis process that uses nonindividualized HRTFs.