EFFECTS ON SOUND LOCALIZATION OF CONFIGURATION AND TYPE OF HEARING IMPAIRMENT

Localization ability of 87 bilaterally hearing-impaired listeners was tested in the horizontal and vertical planes, frontally and laterally. In those with sensorineural hearing loss, it was found that deficits in localization accuracy in different regions of auditory space could be related to different configurations of hearing loss. For example, t here were associations between vertical plane discrimination and high- frequency sensitivity; and front-rear; discrimination and mid-to-high- frequency sensitivity. These results agree with theoretical expectatio ns, while the outcome overall contrasts with previous reports that loc alization performance is unrelated to audiometric configuration. A com parison of 13 listeners with conductive/mixed types of impairment with a sensorineural-loss group, matched for degree of loss', showed that a conductive component adds significantly to localization disturbance, particularly in the horizontal plane. The probable reason is a distur bance of low-frequency interaural time cues, and this occurs because a higher proportion of low-frequency sound is likely to be transmitted via bone conduction relative to air conduction. Correlations between h earing loss and localization are only moderate, suggesting that aspect s of hearing impairment, in addition to simple attenuation, may also r educe auditory localization performance.