Date of Award

Fall 12-15-2023

Level of Access Assigned by Author

Open-Access Dissertation

Language

English

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

Advisor

Xudong Zheng

Second Committee Member

Qian Xue

Third Committee Member

Wilhelm Alex Friess

Additional Committee Members

Nicholas May

Scott Thomson

Abstract

This dissertation aimed to advance knowledge of how subglottal stenosis impacts voice production physiology. An in-house fluid-structure-acoustic interaction approach based on the hydrodynamic/acoustic splitting technique was employed. This technique was rigorously verified for simulating phonation by matching the acoustic behavior to a compressible flow solver for phonation-relevant geometries. Simulations of an idealized 2D vocal tract model demonstrated the effects of supraglottal acoustic resonance on vocal fold kinematics and glottal flow waveform. Results showed that the acoustic coupling between higher harmonics and formats generated pressure oscillations, modifying vocal fold dynamics and glottal flow rate.

A major novelty was the incorporation and systematic parametric study of subglottal stenosis effects on voice production in an idealized 3D laryngeal model for the first time. Variation of subglottal stenosis severity revealed changes in vocal fold motion for severities higher than 90%, and flow rate and acoustics for severities higher than 75%. Detailed analysis revealed relative flow resistance and the ratio between glottal and stenosis minimum areas as primary factors determining the degree of influence. This provided new insights relating stenosis severity to physical changes in voice production consistent with clinical intervention guidelines.

Highly detailed subject-specific realistic laryngeal and vocal tract geometries were reconstructed from high-resolution imaging to enable developing a coupled flow-acoustics-solid interaction model. Self-sustained vocal fold oscillations and glottal flow rates matching human phonation validated this highfidelity model’s capabilities. Parametric stenosis studies provided confirmation using real geometries and additional insights into underlying physical mechanisms.

In summary, this dissertation research verified numerical methods, revealed acoustic resonance effects, systematically quantified stenosis severity thresholds, and elucidated mechanisms relating observations to area ratio and pressure drops. Outcomes significantly advance fundamental knowledge of simulating normal and pathological voice production. This work provides a strong foundation for future translational research on modeling other voice disorders, supporting surgical planning, and guiding interventions.

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