Lateralization of an auditory signal in correlated noise and in uncorrelated noise as a function of signal frequency

Listeners lateralized a monaural signal presented against a continuous background of perfectly correlated noise (NO) or of uncorrelated noise (NU). Measures of signal detectability were also secured in separate tests. Psychometric functions (percent correct vs signal energy) were determined for each task. For a tonal signal of either low or high frequency, a listener requires only slightly greater signal energy (about 1 dB) in order to lateralize as well as he can detect when the noise is uncorrelated (NU). When the noise is perfectly correlated (NO), the slope of the psychometric function for lateralization depends upon signal frequency. With 250 Hz, the slope of the psychometric function for lateralization is much smaller than that for detection. With 1,000 Hz, the function for lateralization is steeper than that for 250 Hz, but the slope is still less than that of the function for detection for 1,000 Hz. With 2,000 Hz, the function for lateralization has about the same slope as that for detection.