ASA 127th Meeting M.I.T. 1994 June 6-10

3aPP6. Consistency over frequency in high-frequency binaural lateralization.

Wonseok Lee

Richard M. Stern

Dept. of Electrical and Comput. Eng. and Biomed. Eng. Prog., Carnegie Mellon Univ., Pittsburgh, PA 15213

Recent experimental results [e.g., R. M. Stern et al., J. Acoust. Soc. Am. 84, 156--165 (1988)] imply that the auditory system emphasizes the contributions of internal delays that are consistent over frequency in lateralizing binaural stimuli. This phenomenon, known as ``straightness weighting,'' has been used effectively to predict lateralization of low-frequency bandpass noise. This paper describes a series of experiments that investigate the extent to which a similar type of straightness weighting is observed at high frequencies for which there is no synchronization of the auditory-nerve response to the fine structure of the stimuli. High-frequency bandpass noise stimuli were generated by summing cosines with interaural time delay (ITD) that were systematically varied as a function of frequency. Stimuli were generated that produce varying amounts of consistency over frequency in the putative response of the units in the binaural system that record interaural coincidences of auditory-nerve activity. The results of pilot experiments in which a rivalry is established between ridges of the response at different internal delays indicate that lateralization for these stimuli is dominated by the component of the high-frequency stimulus that produces the component of the response that is most consistent over frequency. [Work supported by NSF.]