Masking of speech in young and elderly listeners with hearing loss

This study examined the contributions of various properties of background noise to the speech recognition difficulties experienced by young and elderly listeners with hearing loss. Three groups of subjects participated: young listeners with normal hearing, young listeners with sensorineural hearing loss, and elderly listeners with sensorineural hearing loss. Sensitivity thresholds up to 4000 Hz of the young and elderly groups of listeners with hearing loss were closely matched, and a high-pass masking noise was added to minimize the contributions of high-frequency (above 4000 Hz) thresholds, which were not closely matched. Speech recognition scores for monosyllables were obtained in the high-pass noise alone and in three noise backgrounds. The latter consisted of high-pass noise plus one of three maskers: speech- spectrum noise, speech-spectrum noise temporally modulated by the envelope of multi-talker babble, and multi-talker babble. For all conditions, the groups with hearing impairment consistently scored lower than the group with normal hearing. Although there was a trend toward poorer speech-recognition scores as the masker condition more closely resembled the speech babble, the effect of masker condition was not statistically significant. There was no interaction between group and condition, implying that listeners with normal hearing and listeners with hearing loss are affected similarly by the type of background noise when the long-term spectrum of the masker is held constant. A significant effect of age was not observed. In addition, masked thresholds for pure tones in the presence of the speech-spectrum masker were not different for the young and elderly listeners with hearing loss. These results suggest that, for both steady-state and modulated background noises, difficulties in speech recognition for monosyllables are due primarily, and perhaps exclusively, to the presence of sensorineural hearing loss itself, and not to age-specific factors.