Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Communication Sciences and Disorders

First Advisor

M. Jane Collins


The effect of durational differences on the identification of vowel tokens was studied using ten normal hearing and six hearing impaired subjects. Stimuli were synthetically generated and varied in duration of the steady state, durations of the initial and final transitions and F1/F2/F3 location. Listeners were required to identify the given vowel token from a set of ten possible alternatives. The results from the normal hearing group supported the established effects of duration on the perception of vowels. However, these effects were different depending on the frequency locations of F1/F2/F3. Further, changes in the duration of the initial transition had a greater effect than changes in the duration of the final transition. By way of comparison, the identification behavior of the normal hearing subjects was different from the identification behavior of hearing impaired subjects. In particular, the hearing impaired subjects' behavior was idiosyncratic. Further, not only were the subjects different from each other the labelling performance was different within the same subjects across the different vowels. Thus, the effects of durational changes on vowel identification by normal hearing and hearing impaired listeners differs as a function of formant frequency structure. In addition, the effects of durational changes were dependent on the portion of the vowel that was manipulated. Finally, hearing impaired listeners were not like the normal hearing listeners, nor were they like each other. The results, then can be interpreted to indicate that vowel perception by normal hearing and hearing impaired listeners is a complex multi-cued phenomenon.