A binaural analog of gap detection

The temporal resolution of the binaural auditory system was measured using a binaural analog of gap detection. A binaural "gap" was defined as a burst of interaurally uncorrelated noise (Nu) placed between two bursts of inter aurally correlated noise (NO). The Nu burst creates a dip in the output of a binaural temporal window integrating interaural correlation, analogous to the dip created by a silent gap in the output of a monaural temporal windo w integrating intensity. The equivalent rectangular duration (ERD) of the b inaural window was used as an index of binaural temporal resolution. In ord er to derive the ERD, both the shortest-detectable binaural gap and the jnd for a reduction in interaural correlation from unity were measured. In exp eriment 1, binaural-gap thresholds were measured using narrow-band noise ca rriers as a function of center frequency from 250 to 2000 Hz (fixed 100-Hz bandwidth) and as a function of lower-cutoff frequency from 100 to 400 Hz ( fixed 500-Hz upper-cutoff frequency). Binaural-gap thresholds (1) increased significantly with increasing frequency in both tasks, and (2) at frequenc ies below 500 Hz, were shorter than corresponding silent-gap thresholds mea sured with the same NO noises. In experiment 2, interaural-correlation jnd' s were measured for the same conditions. The jnd's also increased significa ntly with increasing frequency. The results were analyzed using a temporal window integrating the output of a computational model of binaural processi ng. The ERD of the window varied widely across listeners, with a mean value of 140 ms, and did not si,significantly depend on frequency. This duration is about an order of magnitude longer than the ERD of the monaural tempora l window and is, therefore, consistent with "binaural sluggishness." (C) 19 99 Acoustical Society of America. [S0001-4966(99)04605-6].