Binaural image position distributions for phase-shifted low frequency tone bursts.

This experiment was designed to yield precise measures of the statistical properties of perceived sound images. Results are reported for listeners' judgments of intracranial sound image lateral positions in response to binaural tone burst stimuli (250 Hz, 50 ms) with varying interaural phase differences, conditional on the absence or presence of a (left or right) reference monaural tone burst (also 250 Hz, 50 ms) ending 500 ms prior to the test signal. The monaural-reference shifted the position distributions toward the opposite side of the head. The position distribution variance and skewness depended on the mean of the position distribution, not on the interaural phase difference of the stimulus. The standard deviation increased as the mean moved laterally from midline. Near the midline the position distributions were skewed ipsilaterally. Near either ear they were skewed toward the midline. The results suggest that the most important noise limiting performance originates central to brainstem coincidence detector networks.