Graduation Year

2008

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Communication Sciences and Disorders

Major Professor

Catherine L. Rogers, Ph.D.

Co-Major Professor

Jennifer J. Lister, Ph.D.

Keywords

Speech perception, Temporal cue, Spectral cue, Sensorineural hearing loss, Presbycusis

Abstract

Older listeners, both with and without hearing loss, often complain of difficulty understanding conversational speech. One reason for such difficulty may be a decreased ability to process the rapid changes in intensity, frequency, or temporal information that serve to differentiate speech sounds. Two important cues for the identification of stop consonants are the duration of the interruption of airflow (i.e., closure duration) and rapid spectral changes following the release of closure. Many researchers have shown that age and hearing loss affect a listener's cue weighting strategies and trading relationship between spectral and temporal cues. The study of trading relationships between speech cues enables researchers to investigate how much various listeners rely on different speech cues. Different cue weighting strategies and trading relationships have been demonstrated for individuals with hearing loss, compared to listeners with normal hearing.

These differences have been attributed to the decreased ability of the individuals with hearing loss to process spectral information. While it is established that processing of temporal information deteriorates with age, it is not known whether the speech processing difficulties of older listeners are due solely to the effects of hearing loss or to separate age-related effects as well. The present study addresses this question by comparing the performance on a series of psychoacoustic and speech identification tasks of three groups of listeners (young with normal-hearing, older with normal-hearing, and older with impaired hearing) using synthetic word pairs ("slit" and "split"), in which spectral and temporal cues are altered systematically.

Results of the present study suggest different cue weighting strategies and trading relationships for all three groups of listeners, with older listeners with hearing loss showing the least effect of spectral cue changes and young listeners with normal hearing showing the greatest effect of spectral cue changes. Results are consistent with previous studies showing that older listeners with and without hearing loss seem to weight spectral information less heavily than young listeners with normal hearing. Each listener group showed a different pattern of cue weighting strategies when spectral and temporal cues varied.

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