Date of Award


Degree Name

Master of Arts


Speech, Language and Hearing Sciences

First Advisor

Dr. John Hanley

Second Advisor

Dr. James Hillenbrand

Third Advisor

Dr. Larry Oppliger

Access Setting

Masters Thesis-Open Access


Pitch and amplitude perturbation values were compared for nine adult stutterers and nine adult nonstutterers. Each subject produced ten sustained phonations of the vowels /a/ and /i/. An automatic pitch-synchronous autocorrelation fundamental frequency tracker was used to extract period and amplitude measures.

Findings revealed that: (a) stutterers had significantly more vocal shimmer than nonstutterers (p = .01), (b) F-ratios for percent jitter between groups approached (p = .07) but did not reach significance, and (c) the vowel /a/ was produced with higher levels of jitter and shimmer than the vowel /i/. Results support the notion that instability of the vocalization process is present in stutterers during fluent utterances. The potential usefulness of acoustic perturbation measures in understanding, diagnosing, and treating the disorder of stuttering is discussed.