Masters Theses

Date of Award

8-1997

Degree Type

Thesis

Degree Name

Master of Arts

Major

Speech Pathology

Major Professor

Patrick J. Carney

Committee Members

Carl Asp, Dolly C. Davis

Abstract

This study sought to determine the differences in vocal fundamental frequency perturbation, or jitter, between two groups of female subjects. Ten trained female singers and ten female speakers with no formal training or singing experience sustained an /a/ vowel for four seconds at two levels of fundamental frequency--the subject's speaking fundamental frequency (SFF) and an octave above SFF--and three levels of intensity: 60, 70 and 80 dB SPL measured at a microphone-to-mouth distance of 12". For each vowel token, intensity and frequency were monitored to maintain experimental criteria, and the vowel samples were digitally analyzed to obtain vocal jitter expressed as relative average perturbation (RAP) in percent. Mean jitter values were compared across frequency, intensity and group factors using an analysis of variance technique.

The trained singers demonstrated no significant change in mean jitter from SFF to one octave above SFF, or from 70 dB to 80 dB. In contrast, the untrained singers demonstrated a significant increase in vocal jitter with frequency, and a significant decrease in jitter with intensity. Both subject groups had increased jitter magnitudes and variability at the 60 dB condition, especially at the lower fundamental frequency, which is consistent with the conclusions of other investigators. The major conclusion of this study is that the trained singers produced stable phonation regardless of frequency or intensity, while the untrained subjects' phonation stability varied significantly with changes in frequency and intensity. This finding suggests a difference between trained and untrained voices in the vocal dynamics of frequency and intensity control.

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