Gap duration discrimination in listeners with cochlear hearing loss: effects of gap and marker duration, frequency separation, and mode of presentation.

This study examined the effects of cochlear hearing loss on gap duration discrimination (GDD), with particular interest in whether cochlear hearing loss results in increased difficulty for across-channel temporal judgments. The hypothesis being tested was that listeners with cochlear loss would perform as well as normal-hearing listeners for all within-channel conditions but would exhibit relatively greater performance deficits in the across-channel conditions. A subsidiary aim was to determine whether, in normal-hearing listeners, the across-channel effects previously observed for minimal-duration standard gaps also existed for relatively long standard gaps. Two experiments were undertaken, one dealing with monaural conditions and one dealing with dichotic conditions. The monaural results indicated that across-frequency GDD was poorer than isofrequency GDD, even for the longer gap durations of 35 and 250 ms examined here. However, the results showed no effect of hearing loss on GDD. Rather, GDD appeared to be sensitive to listener age, with younger listeners showing better performance in both within-channel and across-channel conditions. In addition, both within-channel and across-channel performance was sensitive to the duration of the leading gap marker. Finally, the pattern of dichotic "across-ear" performance was similar, but not equivalent, to that of monaural across-frequency performance.