FREQUENCY ANALYSIS IN NORMAL AND IMPAIRED LISTENERS

The primary evidence of reduced frequency selectivity in listeners with
sensorineural hearing loss comes from masking studies where these listeners
are found to have abnormally high thresholds and abnormally poor speech
perception. This proposal outlines a series of studies designed to test
the hypothesis that the effect of hearing loss combines with the effect of
an external masker in the same way that the effect of one external masker
combines with the effect of another. Recent research suggests that most
combinations of external maskers produce more masking in listeners with
normal hearing than would be predicted from the effects of the individual
maskers and that the rules governing effects of combined maskers differ for
different types of maskers. Recent models of additivity of masking provide
a framework for integrating these diverse results which could be expanded
to include effects of sensorineural hearing loss. The proposed work
includes further development of models of additivity, further studies of
additivity in both normal and impaired listeners, and studies to extend
this approach to encompass loudness growth and speech perception. Hearing
loss and masking are clearly not equivalent. Learning more about precisely
how they differ will lead to a better understanding of both processes and
of how they interact with one another.