Refinement and Characterization of Synthetic Vocal Fold Models

• Main Author: Ward, Shelby Charisse
• Format: Others
• Published: BYU ScholarsArchive 2014
• Subjects: vocal fold; voice; stiffness; asymmetry; geometry variation; Mechanical Engineering
• Online Access: https://scholarsarchive.byu.edu/etd/4225; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=5224&context=etd

Understanding vocal fold mechanics is an integral part of voice research and synthetic vocal fold models are an essential tool in characterizing vocal fold mechanics. These models contain multiple layers with varying stiffness, much like human vocal folds. The purpose of this thesis is to improve the current models and modeling techniques, as well as investigate the impact of asymmetry on model vibration. A new design for an MRI-based model is detailed. This model has a more realistic geometry than the simplified models and mimics some of the vibratory characteristics observed in human vocal folds. The MRI-based model was used to investigate left-right stiffness asymmetry in multiple layers of the model. A zipper-like motion was observed during vibration of the MRI-based models. A phase shift was present in the asymmetric models, with the less stiff side leading the stiffer side. A new expendable mold fabrication process is described. This new process provides more freedom in designing vocal fold models and experiments. Additionally, the new process enables fabrication of models without the use of release agent, a factor which has, in the past, adversely impacted manufacturing yield and prohibited the incorporation of certain biological materials into the synthetic models. The new process also allows for more convenient geometry variation than what has previously been feasible. Finally, the new process was used to investigate cover layer geometry variation and asymmetry in a simplified model. Cover layer thickness was found to be a significant factor in governing the motion of the vocal fold model. Anterior-posterior asymmetry was found to induce the same zipper-like motion observed in the MRI-based models.