Laura Smith
Janet Koehnke
Joan Besing
Dept. of Commun. Sci. and Disord., Louisiana State Univ., 163 M&DA, Baton Rouge, LA 70803
The ability to discriminate interaural differences in complex signals was examined in listeners with normal hearing and with bilateral sensorineural hearing impairment. Just noticeable differences (jnds) for interaural time and interaural intensity were obtained using 1/3-octave narrow band noise (NBN) stimuli centered at 500 and 4000 Hz in three conditions. In condition 1 the NBNs were played in isolation; in condition 2 the NBNs were played simultaneously with congruent interaural information across frequency; and in condition 3 the NBNs were played simultaneously with either the 500-Hz band dichotic and the 4000-Hz band diotic (3a) or the 500-Hz band diotic and the 4000-Hz band dichotic (3b). The best interaural time and intensity discrimination for the listeners with impaired hearing is seen when both bands contain congruent interaural information (condition 2). Subjects with impaired hearing and normal hearing show reduced sensitivity to interaural time differences when the 500-Hz band is diotic and discrimination is based on the 4000-Hz band (3b). The listeners with impaired hearing also demonstrate poorest interaural intensity discrimination for this condition (3b). Results suggest that subjects with impaired hearing may benefit from congruent interaural information in more than one frequency region. [Work supported by the Dept. of Veterans Affairs and NIH Grant No. DC00428.]