The index of interaural correlation: Accounting for binaural detection across center frequency.

Abstract

Investigations in this laboratory demonstrated that the normalized correlation accounted well for listeners’ performance in binaural tasks utilizing high‐frequency stimuli for which the envelopes convey the interaural information. This outcome means that the non‐zero mean of the envelopes must be included in the computation of the correlation. Due to peripheral auditory processing analogous to rectification and low‐pass filtering, the ‘‘internal’’ representations of auditory stimuli have nonzero means regardless of their frequency. This study evaluated whether the normalized correlation computed subsequent to rectification and low‐pass filtering could account for detection data at low and intermediate, as well as high frequencies. In a four‐interval, two‐alternative task, listeners detected which interval contained a tone (between 500 Hz and 2 kHz) added antiphasically to diotic, 100‐Hz‐wide, noise (NoSπ). ‘‘Nonsignal’’ intervals contained the tone added homophasically (NoSo). Performance was measured for S/Ns between −30 and +30 dB. For all S/Ns, overall level was 70 dB SPL. Normalized correlation (unlike the correlation coefficient) described performance well, as a function of S/N and center frequency. The parameters of the rectifier and low‐pass filter required to describe the data will be discussed. [Supported by research Grant No. 5R01DC0210302, National Institute on Deafness and Other Communication Disorders, NIH.]