The project proposes a program of studies in speech perception and auditory psychophysics to examine the hypothesis that many of the predominant difficulties in speech understanding for elderly listeners are related to underlying problems in auditory temporal processing. Research indicates that elderly listeners have particular problems recognizing speech that is degraded by alteration of speaking rate and/or reverberation, with rapid speech eliciting the strongest age-related processing deficits. The listeners' difficulty in understanding temporally-altered speech may be attributed to deficits in peripheral sensory mechanisms, centrally mediated timing mechanisms, and age-related changes in cognitive function. The project investigates the relative contributions of peripheral hearing impairment, degree of stimulus temporal complexity, and altered cognitive demands on auditory processing using rate-altered speech and non-speech stimulus sequences. The project comprises four stages of investigation, each consisting of a series of speech recognition experiments and psychoacoustic temporal discrimination and identification tasks. Stage 1 (mos. 1-18) investigates the principal temporal factors contributing to processing deficits associated with rate-altered speech sentences and non-speech sequential patterns. Stage 2 (mos. 13-36) examines the effects of varying stimulus temporal complexity and rate alteration on recognition and discrimination of speech and non-speech sequential sequences. Stage 3 (mos. 30-48) evaluates the effects of time alteration on enhancement of speech recognition and recall of speech and non-speech stimulus sequences. Stage 4 (mos. 49-60) examines the benefits of time-alteration enhancement techniques for recognition of speech and non-speech sequences of varying rhythmic complexity. For each stage of the investigation, the independent effects of cognitive demands, subject age, and hearing loss on listener performance will be examined. Subjects in the project will include young and elderly listeners with normal hearing and matched degrees of sensorineural hearing loss. All subjects will be examined as well on educational background, physical and mental health and otologic history.
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