ASA 124th Meeting New Orleans 1992 October

1aPP7. Auditory spectral cues for the resolution of front--back confusion in humans.

Simon Carlile

Daniele Pralong

Univ. Lab. of Physiology, Oxford OX1 3PT, UK

The interaural level and timing difference cues are ambiguous for sound location and give rise to the so-called cones of confusion. Psychophysical work has demonstrated that spectral cues furnished by the auditory periphery are critical for resolving these front--back ambiguities. The transfer functions were recorded from each auditory canal in human subjects for 365 locations in anechoic space. For anterior locations there are substantial gains around 3--4 kHz and above 13 kHz and a notch in the transfer function that moves up in frequency (8 to 12 kHz) for locations away from the midline. These features remain reasonably consistent over a 60(degrees) change in elevation about the interaural horizontal plane (IAP). For posterior sound locations, transmission is relatively flat for locations below the IAP but a sharp notch centered on 9 kHz is evident for locations above the IAP. The changes in the interaural spectral differences are relatively symmetrical for horizontal locations about the interaural axis, although at high frequencies (>12 kHz) there are some features that might provide front--back information for locations close to the interaural axis. These acoustical data identify several spectral features in the human monaural transfer functions that may provide potent, unambiguous cues to a sounds location. [Work supported by the Beit Foundation, McDonnel Pew Centre for Cognitive Neurosciences, Swiss National Science Foundation, and Foundation for the 450th Birthday of the University of Lausanne.]