Discriminability of interaural time disparities by normal and hearing‐impaired listeners

Abstract

Thresholds of on‐going interaural time difference (ITD) were obtained from normal‐hearing and hearing‐impaired subjects who had high‐frequency, sensori‐neural hearing loss. Utilizing several stimuli (a 500‐Hz sinusoid, a narrow‐band noise centered at 500 Hz, a 4000‐HZ tone amplitude‐modulated at 250 Hz, and a narrowband noise centered at 4000 Hz), four criteria for determining the level of presentation to each subject were employed: (1) Equal sound pressure level; (2) equal sensation level; (3) equal loudness; and (4) midline intracranial image. The ITD thresholds and slopes of the psychometric functions were elevated for hearing‐impaired subjects for the two high‐frequency stimuli in comparison to: (1) The subject's own low‐frequency thresholds and (2) data obtained from normal‐hearing subjects for stimuli presented with equal SPL interaurally. The ITD thresholds using stimuli level based on equal loudness and a centered image were slightly lower than those obtained using the equal SPL criterion.