Theresa Smith

Date of Award


Degree Name

Master of Arts


Speech, Language and Hearing Sciences

First Advisor

Dr. Gary Lawson

Second Advisor

Dr. Hal Bate

Third Advisor

Dr. John Hanley

Access Setting

Masters Thesis-Open Access


The purpose of the study was to identify within-group and between-group differences in perceived quality and perceived intelligibility of degraded speech for listeners with normal and impaired hearing. Following a visual magnitude estimation task, 10 subjects with normal hearing and 10 subjects with sensory-neural hearing impairment listened to connected speech samples degraded by seven levels of harmonic distortion and estimated the magnitude of their quality and intelligibility. Log average quality estimates and log average intelligibility estimates varied linearly with log degradation values for each group. The slopes of the log-log functions were interpreted as measures of perceptual sensitivity. Slopes for each listening task varied considerably within each listener group. Differences among the slopes were not statistically significant as a function of groups, tasks, or interaction of groups and tasks. The results were compared with those of related studies and implications for future research were presented.