DO ADAPTIVE FREQUENCY-RESPONSE (AFR) HEARING-AIDS REDUCE UPWARD SPREAD OF MASKING

Speech recognition scores in noise are improved for some subjects who wear hearing aids that reduce low-frequency noise with an adjustable h igh-pass filter circuit. To evaluate whether these improvements were r elated to a reduction in upward spread of masking, pure-tone masking p atterns for a low-frequency bandpass noise were measured in normal and hearing-impaired subjects. The filter skirt of the noise masker was v ery steep, with attenuation above the 1000 Hz cutoff greater than 120 dB per octave. Masking patterns for the same noise were also obtained in the presence of a high-pass filter that simulated the effects of an adaptive frequency response (AFR) hearing aid. Differences in the mas king patterns were considered a measure of upward spread of masking. O n average, subjects with high-frequency hearing loss demonstrated grea ter amounts of upward spread of masking than did normal-hearing listen ers. Further, monosyllabic speech recognition in noise testing indicat ed improvements in performance of the hearing-impaired subjects relate d to the decrease of upward spread of masking in the high-pass filteri ng conditions.