Recognition of temporally distorted words by listeners with and without a simulated hearing loss.

In separate experiments, word recognition performance of two groups of 12 normal-hearing young adults was investigated as a function of temporal distortion (i.e., time compression ratio or reverberation time) with and without a simulated high-frequency hearing loss (i.e., low-pass filtered at 2000 Hz). Performance decreased significantly as a function of increasing time compression, reverberation, and with the simulated hearing loss (p < .05). A statistically significant interaction between each of time compression ratio and reverberation time with the filtered listening condition was found (p < .05). This finding of an interactive, as opposed to a simple additive, effect of multiple distortions of the speech on word recognition performance suggests that loss of audibility alone cannot account for decrements in word recognition performance with time-altered speech. It is suggested that this multiplicative effect for combined acoustic distortions is a consequence of the functional loss of the high-frequency region of the cochlea. Not only is there a loss of audibility, but there is also a loss in temporal resolution capacity since it is perception mediated through the population of high-frequency auditory channels that has the best temporal resolution.