Discrimination of interaural temporal disparities by normal-hearing listeners and listeners with high-frequency...

Thresholds of ongoing interaural time difference (ITD) were obtained from normal-hearing and hearing-impaired listeners who had high-frequency, sensorineural hearing loss. Several stimuli (a 500-Hz sinusoid, a narrow-band noise centered at 500 Hz, a sinusoidally amplitude-modulated 4000-Hz tone, and a narrow-band noise centered at 4000 Hz) and two criteria [equal sound-pressure level (Eq SPL) and equal sensation level (Eq SL)] for determining the level of stimuli presented to each listener were employed. The ITD thresholds and slopes of the psychometric functions were elevated for hearing-impaired listeners for the two high-frequency stimuli in comparison to: the listener's own low-frequency thresholds; and data obtained from normal-hearing listeners for stimuli presented with Eq SPL interaurally. The two groups of listeners required similar ITDs to reach threshold when stimuli were presented at Eq SLs to each ear. For low-frequency stimuli, the ITD thresholds of the hearing-impaired listener were generally slightly greater than those obtained from the normal-hearing listeners. Whether these stimuli were presented at either Eq SPL or Eq SL did not differentially affect the ITD thresholds across groups.