Communication Disorders Ph.D. Dissertations

The Effect of Nonlinear Source-Filter Interaction on Aerodynamic Measures in a Synthetic Model of the Vocal Folds and Vocal Tract

Date of Award

2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Communication Disorders

First Advisor

Ronald Scherer (Committee Chair)

Second Advisor

Joseph Furgal (Other)

Third Advisor

Brent Archer (Committee Member)

Fourth Advisor

Lewis Fulcher (Committee Member)

Fifth Advisor

Jason Whitfield (Committee Member)

Abstract

According to nonlinear source-filter theory, as the strength of the coupling between the source and filter increases, typically by a decrease in the vocal tract cross sectional area, the resultant increase in the inertance of the vocal tract yields an increase in the interactions between acoustic pressures within the vocal tract and the changing glottal airflow and/or the vibratory pattern of the vocal folds. The purpose of the current research was to examine the effects of parametric vocal tract constrictions mimicking epilaryngeal tube and lip narrowing on aerodynamic and projected glottal area measures in a dynamic self-oscillating physical model of the vocal folds and vocal tract. Multilayered silicone vocal fold models were created (after Murray & Thomson, 2011, 2012) and mounted to a simple synthetic trachea and supraglottal vocal tract model. Four constriction cross sectional areas were examined at two locations yielding 16 possible experimental vocal tract conditions. Vocal fold model adduction and tension were held constant across all experimental conditions; three constant subglottal pressures were examined. Results indicate that: 1) mean phonation threshold pressure (PTP) at onset and offset, phonation instability pressure (PIP) onset, phonation pressure range (PPR) onset, phonation threshold flow (PTF) at onset and offset, phonation instability flow (PIF) onset and offset, and phonation flow range (PFR) onset and offset were all found to generally decrease given a constriction in the epilarynx tube region; 2) mean PIP offset, and PPR offset were all found to generally increase given a constriction in the epilarynx tube region; 3) mean PTP at onset and offset and PTF at onset and offset were all found to generally decrease given a constriction in the lip region; and 4) mean PIP onset and offset, PPR onset and offset, PIF onset and offset, and PFR onset and offset were all found to generally increase given a constriction in the lip region. Thus, results indicate that both constriction magnitude and location are relevant factors in determining glottal aerodynamics and projected glottal area measures.

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