Abstract

Approximately 7.5 million people suffer from voice disorders in the United States. Previous studies indicate that the quality of the fluid layer that coats the vocal folds appears to be different for people with voice disorders than for people whose voice is considered normal. These studies suggest that the composition and/or physical properties of the fluid layer may contribute to voice disorders. Despite these findings, little research has been undertaken to investigate the role of the fluid layer on voice, and in almost all cases, the fluid layer is considered to be insignificant. The purpose of this research was to investigate the role of the fluid layer and the potential it may have to influence voice production; particularly, to identify some aspects of the fluid layer that have the potential to contribute to voice disorders. In order to investigate the potential significance of the effects of a fluid layer on vocal fold operation, an existing lumped model was modified to incorporate the Newtonian squeeze-flow equation as a fluid model during the colliding portion of the oscillatory cycle. Results indicated that thicker films produced more significant deviations from the case with no fluid layer. Experimental testing was performed to validate existing analytical equations for squeezing flow of Newtonian and non-Newtonian fluids confined between parallel axisymmetric plates. Based on available published data on the rheological properties of the fluid layer found on the surface of the vocal folds, several fluids with a range of fluid properties were selected. Reasonable agreement was found for much of data collected for the Newtonian fluid cases within measurement tolerances. For the non-Newtonian cases, the constitutive equation was found to be in poor agreement with the measured physical characteristics of the selected non-Newtonian fluids. A summary of the collected experimental data is provided so that it can be used in for validation and comparison in future research. A preliminary computational model based on the classical two-mass vocal fold model was implemented which incorporated squeezing effects of a thin Newtonian film of fluid on the surface of the vocal folds. Results indicated that the fluid layer may not be insignificant, although further tests and modeling are required. Finally, different fluids were applied to a physical model of the vocal folds and measurements were taken to determine the effects of the application of fluid. The results showed significant changes in the vocal fold model response that indicated the fluid layer affects vocal fold operation in important ways. Some of the changes in response could not be attributed solely to the fluid layer. Suggestions regarding future work with physical model testing are given which may help clarify the effects of a fluid layer on vocal fold flow-induced vibration.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering

Rights

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