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. Of the many forms of degraded speech observed to be difficult for elderly listeners, those that involve an alteration of speech rate appear to produce the largest age-related recognition deficits. Alterations of speech rate may be viewed as a form of degradation in temporal aspects of speech segmental cues and speech prosody, and these types of distortions are the focus of investigation in the next project period. Moreover, psychoacoustic results demonstrate that large age-related difficulties in temporal processing exist for the perception of auditory tempo and rhythmic characteristics of sequential stimulus patterns. Listener processing difficulty could be attributed to peripheral and/or central processing mechanisms, as well as various cognitive factors, including the degree of familiarity with prosodic features of different native languages. The project examines the relative contribution of peripheral hearing impairment, type of stimulus temporal complexity and cognitive demand on the processing of temporal segmental and prosodic cues in speech and non-speech stimulus patterns. The project comprises four stages of investigation, each consisting of a series of speech and non-speech discrimination and recognition tasks. Stages 1 and 2 investigate the sources of age-related differences in temporal sensitivity for discriminationand identification of speech and non-speech segments presented as isolated target stimuli or as embedded in sequential stimulus patterns. Stage 3 measures the influences of listener age on discrimination of temporal cues for prosody that characterize different languages. Stage 4 will examine psychoacoustic models of temporal processing and identify stimulus parameters contributing to age-related differences in understanding accented English. Participants in the project will include groups of subjects that differ by age and hearing sensitivity.
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