Auditory brainstem and middle latency responses to 1 khz tones in noise-masked normally-hearing and sensorineurally hearing-impaired adults.

The present study provides comparative evaluation of the ABR and MLR to 1 kHz brief tones in two groups of hearing-impaired subjects (noise-masked normally-hearing; and sensorineurally hearing-impaired adults), as well as a normally-hearing control group. Tones were presented at intensities from threshold to 80-90 dB nHL. The results of this study show that: (1) the ABR and MLR to these low-frequency (1 kHz) tones are equally accurate in estimating hearing threshold, (2) at supra-threshold levels, there are differences in the ABRs and MLRs for subjects with decreased hearing sensitivity resulting from cochlear pathology, compared to those obtained from adults with simulated hearing loss due to broadband masking, and (3) supra-threshold stimuli produce differential effects on the latency and amplitude characteristics of the ABR and MLR in listeners with true sensorineural hearing impairments. Possible physiologic explanations are offered for this differential pattern of results.