It has been hypothesised (Moore 1976) that vocal fold pathology will manifest itself in voiced sounds when vibratory characteristics are disrupted. This thesis examines the effects that pathologies have on the vocal folds through the use of a computer simulation model of the human phonatory system. A damped, nonlinear, multiple-mass spring model combined with a transmission line vocal tract model, was developed and mathematically simulated on a computer. Configurational parameters were then varied asymmetrically in order to examine the vibratory characteristics of the system. In particular, the glottal flow and speech signals from the glottal and vocal tract subsystems were observed for perturbations. Next, jitter, shimmer, and harmonics to noise ratio analyses were made and the results compared to a database of analysed speech recordings from Vancouver General Hospital. Finally, an approximate mathematical analysis was made examining the underlying nonlinear oscillatory phenomena. The study showed that the model, a hybrid between the simple two mass Ishizaka and Flanagan model (1972) and the more complex Titze (1973, 1974) model, was able to simulate the desired asymmetrical conditions. Perturbation phenomena were successfully simulated and the results found to be in good agreement with both real data and data obtained from previously published models. The mathematical analysis revealed the observed perturbations to be characteristic of second and third order subharmonics found in nonlinear oscillatory systems. It was also shown that the driving forces discussed by Titze (1980) (ie the Bernoulli effect, vertical phasing and vocal tract loading) all appear directly in the proposed dynamical equation. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 83-88).

Thesis (B.Sc)--University of Hong Kong, 2005. / "A dissertation submitted in partial fulfilment of the requirements for the Bachelor of Science (Speech and Hearing Sciences), The University of Hong Kong, June 30, 2005." Also available in print.

Thesis (B.Sc)--University of Hong Kong, 2007. / "A dissertation submitted in partial fulfilment of the requirements for the Bachelor of Science (Speech and Hearing Sciences), The University of Hong Kong, June 30, 2007." Includes bibliographical references (p. 29-30). Also available in print.

Thesis (M.S.)--Bowling Green State University, 2009. / Document formatted into pages; contains ix, 48 p. : ill. Includes bibliographical references.

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2007. / Includes bibliographical references (p. 113-116).

Thesis (B.Sc)--University of Hong Kong, 2005. / "A dissertation submitted in partial fulfilment of the requirements for the Bachelor of Science (Speech and Hearing Sciences), The University of Hong Kong, June 30, 2005." Also available in print.

Thesis (M.S.)--Brigham Young University. Dept. of Communication Disorders, 2007. / Includes bibliographical references (p. 58-60).

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 101-107).

Phonation onset and offset are important aspects of singing and speech. Their execution requires control of timing and coordination of complex vocal fold kinematics, glottal configuration, laryngeal muscular adjustments, and respiration. The purpose of this study was to examine effects of timing and coordination of vocal fold adductory and abductory movements on vocal fold vibratory behavior from offset to onset in a series of repeated phonation gestures, using high-speed digital imaging. Of particular interest were differences in vocal fold adductory positioning for slower and faster tempi; patterns of oscillation during onset and offset for the different tempi, and effects of onset and offset timing events on subsequent vibratory patterns. Method: 11 subjects, all classically trained, experienced professional singers, were videoendoscopically recorded singing a series of repeated notes at two different tempi, using high-speed digital imaging. Vocal fold adductory positioning was measured in terms of relative glottal width during onset in slower and faster tempi. Vocal fold vibratory behavior was measured in timing of offset and onset “events,” number, spacing, and timing of PPOs and pSSOs. Results: Relative glottal widths were significantly smaller for the faster tempo, supporting a hypothesis that vocal agility requires closer vocal fold approximation before onset. Significant differences were found in offset vs. onset timings and numbers of prephonatory and post-steady-state oscillations, supporting a theory of oscillation hysteresis.