Lateral position and interaural discrimination: Data and blackbox model

Abstract

Experimental results are described for the dependence on interaural stimulus parameters of subjective lateral position and just-noticeable differences in interaural amplitude and time. The experiments employed 500-Hz tones presented through acoustically monitored headphones [R. H. Domnitz, J. Acoust. Soc. Am. 58, 510–511 (1975)] at 55 dB SPL. The overall amplitudes of the stimuli in the interaural amplitude discrimination experiment were iteratively adjusted to eliminate subjective loudness cues. Performance in the experiments is analyzed within the framework of a probabilistic subjective lateralization model in which internal noise is explicitly treated. One prediction of the model relates the ratio of the interaural time and amplitude jnd's to subjective position. Although the data are qualitatively consistent with this prediction, there is close quantitative agreement for only one of three subjects. The model also predicts values of the internal noise of the subjective image position and these are in qualitative agreement with reports of image diffuseness as a function of interaural parameters. Nontradability between large increments of interaural amplitude and time is implied by the experimental results, and can be interpreted in the model as discrimination between tones with equal position means but different position variances. [Work supported by NIH.]