Effects of sensorineural hearing loss on interaural discrimination and virtual localization.

Cross-frequency binaural processing was investigated in listeners with normal hearing (NH) and with bilateral high-frequency sensorineural hearing impairment (IH). In experiment 1 just-noticeable-differences for interaural time and interaural intensity were measured using 1/3-octave narrow-band noises (NBNs) centered at 0.5 and 4 kHz. These stimuli were presented in isolation and in different cross-frequency interaural combinations. IH listeners displayed the best interaural time discrimination when the 0.5-kHz NBN was dichotic and the best intensity discrimination when both bands were dichotic. Both NH listeners (time) and IH listeners (time and intensity) displayed the poorest interaural discrimination when the NBNs were presented simultaneously with interaural differences in only the 4-kHz NBN (0.5 kHz NBN dichotic). Localization accuracy was measured in experiment 2 using the 0.5- and 4-kHz NBNs in isolation and with 0.5-kHz target/4-kHz interferer and 4-kHz target/0.5-kHz interferer conditions. Best localization of NH and IH subjects was seen for the 0.5-kHz target, with or without an interferer. Poorest localization of IH subjects was observed for the 4-kHz target and 0.5-kHz interferer. Results suggest that for these IH subjects, localization is most difficult when they are forced to rely on interaural information in a higher-frequency region with conflicting interaural information at low frequencies.