Masking and partial masking in listeners with a high-frequency hearing loss

3 listeners with sensorineural hearing loss ranging from moderate to moderate-severe starting at frequencies higher than 1 kHz participated in two masking experiments and a partial masking experiment. In the first masking experiment, fM = 1 KHz and LM = 50 dB SPL, higher than normal masked thresholds were obtained for listeners whose hearing was impaired in the frequency region of clear hearing loss as well as in the region of near-normal absolute thresholds. The second masking experiment showed that for hearing-impaired listeners the elevation of the masked thresholds, in decibels, in this frequency region of "near-normal' absolute thresholds was equal to the elevation of the absolute thresholds, in decibels. The third experiment, a partial masking experiment with fM = 975-1025 Hz and LM = 75 dB SPL, showed similar partial-masking functions for hearing-impaired and normal listeners, but the functions for the hearing-impaired listeners were at much higher levels of the partially masked probe tone. Thus the higher masked thresholds of the hearing-impaired can result in a dramatic reduction of the dynamic range of hearing under masking in the frequency region of the hearing loss and also in the region with only a small hearing loss (less than 30 dB). It is suggested that this may explain the speech perception difficulties which these listeners experience, especially in the presence of ambient noise.