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.]