| dc.description | Temporal resolution of cochlear output channels in normal and hearing-impaired listeners was examined. Performance-intensity functions for word recognition were obtained in competing continuous and interrupted broadband noise as a function of signal-to-noise ratio (S/N). In the first experiment, normal-hearing listeners were investigated with and without a simulated high-frequency hearing loss (i.e., lowpass filtering at 2000 Hz). Word recognition improved with increasing S/N and was greater in the interrupted compared to the continuous noise. Performance was inferior with the simulated high-frequency hearing loss, relative to unfiltered listening, only in the interrupted noise condition. It was hypothesized that this performance deficit reflected a reduced ability to temporally resolve auditory information between the bursts of noise as a consequence of reduced available auditory bandwidth. The effect of sensation level (30 vs. 50 dB) on performance in the same paradigm was explored in the second study. An effect of presentation level on word recognition performance was found in only the interrupted noise. Performance was superior at 50 dB SL. These findings suggest different processes underlying word recognition under the two maskers: spectral audibility vs. temporal masking in the continuous and interrupted noise, respectively. In the third experiment performance was compared between young normal-hearing (YNH), cognitively-intact older normal-hearing (ONH), and aged-matched presbycusic listeners (OHI). The YNH group's performance was superior, followed by the ONH and OHI for both noise conditions. It was speculated that the differences in performance were a consequence of either reduced auditory bandwidth available to the older participants, inherent peripheral or central distortion in the older auditory system, nonauditory central effects and/or an interaction of these effects. A fourth experiment, revealing that normal-hearing listeners performance in continuous and interrupted noise was not worse with a simulated high frequency hearing loss (i.e., lowpass filtering at 4000 Hz) vs. without, diminished the appeal of the first suggestion. It is suggested that the dichotomization of young versus old and normal-hearing versus hearing-impaired, albeit convenient and sensible, is likely oversimplified and possibly misleading. The relationship that one may envision is a progressive deterioration of auditory threshold and suprathreshold processing with age. | en_US |
