AUDITORY FILTER SHAPES OF NORMAL-HEARING AND HEARING-IMPAIRED LISTENERS IN CONTINUOUS BROAD-BAND NOISE

Listeners with sensorineural hearing impairment typically exhibit audi tory processing deficits such as reduced frequency and/or temporal res olution. Such deficits may represent separate sequela of auditory path ology or may result directly from the sensitivity loss and the require ment to listen at high levels. To assess the impact of increased thres holds on frequency resolution, auditory filter characteristics were de termined for hearing-impaired and normal-hearing listeners at 500 and 2000 Hz in the presence of continuous broadband noise meant as a rough simulation of hearing loss. In the fitting procedure, the low-frequen cy skirt of the derived auditory filter was allowed to vary as a funct ion of signal level, permitting different filter shapes to be estimate d at high versus low signal levels. Listeners with moderate hearing lo sses at 2000 Hz demonstrated near-normal auditory filter shapes for lo wer signal levels, but increasingly broad and asymmetric filters as si gnal level was raised. At 500 Hz, where hearing losses were mild, filt er bandwidths increased little at the higher signal levels. The presen ce of broadband noise had essentially no effect on filter shapes of ei ther listener group. The filter shape abnormalities demonstrated by li steners with moderate hearing loss, which were not observed in normal- hearing listeners at the same signal levels, indicate that poor freque ncy resolution in these patients for high-intensity stimuli does not f ollow directly from decreased sensitivity, but instead reflects an ind ependent pathology.