Effect of Noise Correlation on Binaural-Signal Detection

Abstract

This is an extension of a study of the effect of the interaural correlation for a masking noise upon the masked threshold for a 500-cps tone as reported in 1961 by Robinson and Jeffress. At that time, comparisons were made between thresholds obtained under both homophasic and antiphasic conditions. However, the variability associated with the threshold measurements (obtained by the constant method) was such as to obscure possible differences between the two antiphasic conditions or between the two homophasic. The present study employs a method derived from the theory of signal detection to obtain a more stable measure of the effects of interaural-noise correlation. Performance was measured in a two-interval forced-choice experiment. The signal levels required for a predetermined value of d′ were obtained for the various conditions from functions relating d′ toE/No. Such signal levels, when plotted as masking level differences (MLD's) relative to the homophasic condition at the 1.0 value of the noise correlation, permit comparisons with similar data obtained by a threshold procedure. The results show, as did the results of the earlier study, a very rapid increase in masking as the correlation is reduced from unity for the antiphasic conditions and a gradual decrease in masking for the homophasic conditions with the same shift in correlation. In addition, the functions relating d′ to E/No show large differences in slope between the antiphasic and homophasic conditions.