This master‘s thesis deals with computational modelling of human vocal folds in phonation position using finite element method. There are described larynx anatomy, voice generation theories and overview of so far published computational models of vocal folds. Next part of the paper deals with a redesign of vocal folds and soft tissues‘ geometry, creation of finite element mesh and implementation of active stress in thyroarytenoid muscle. The problem was solved using Ansys 19.2 software. Computation of stress and deformation of soft tissues in phonation position has been made for 7 variations with different combination of active cartilages and muscles. Lastly, there was evaluated an effect of different cartilages and active muscle stress to final stress and deformation of soft tissues of vocal folds.

<p>There is a considerable body of evidence suggestive that dehydration can negatively impact voice production. However, our understanding of the underlying biology and physiological changes, particularly at the molecular level,  that contribute to this dysphonia are limited. Further, our ability to assess underlying changes in humans is restricted largely to post-mortem tissue or tissue resected during interventional vocal fold surgery, both of which are subject to bias in age and disease state. Here we have utilized a New Zealand white rabbit model of vocal fold dehydration to probe the <em>in vivo</em> molecular response to dehydration, focusing on differential gene and protein regulation. In the first study, a single 8-hour exposure to low humidity was used to induce airway surface dehydration. RNA Sequencing was used to obtain a global snapshot of differential transcriptional regulation. This informed a second study wherein 8-hour exposures to low humidity over 15 consecutive days were used and followed by LC-MS/MS proteomic analysis to interrogate potential functional changes. In the third study, systemic dehydration was induced with a 5-day water restriction protocol. A third rehydrated group was included that returned to <em>ad libitum</em> consumption for 3 days. LC-MS/MS proteomic analysis was used. We have found evidence for transcriptional and protein expression changes under both dehydration paradigms. Our findings serve to inform our molecular biological understanding of dehydration of the vocal folds with implications to prophylaxis against and clinical intervention thereof. </p>

The purpose of this research was to study perfusion pressure-flow relationships in self-oscillating synthetic poroelastic vocal fold (VF) models before, during, and after vibration. This was accomplished by developing a custom ultra-soft poroelastic material, incorporating the poroelastic material as the cover layer in a synthetic VF model, and studying the model vibratory response and the flow rate of fluid perfused through the cover layer while undergoing flow-induced vibration. The custom ultra-soft poroelastic material was developed using the method of direct templating with sucrose spheres as the sacrificial template and silicone as the infiltration medium. The average modulus of elasticity of the poroelastic material was found to be 3.30 kPa, which represented an 84% decrease compared to the same non-porous silicone. Porosities between 62.8% and 67.2% were estimated. The fabrication process of the poroelastic VF model is presented in detail, including steps to prepare the model for vibration. The apparatus for measuring perfusion pressure flow-relationships in the VF model is described. Vibratory characteristics of subglottal onset pressure, frequency, glottal area, and glottal width are presented and compared to those of the human VF and other published VF models for varying perfusion pressures. The effects of vibration on perfusion flow rate and permeability are reported. The poroelastic VF models had an average onset pressure of 1.01 kPa while vibrating at an average frequency of 117 Hz and with a glottal width of 1.40 mm. Perfusion flow rate decreased between 15% and 22% from rest to vibration and increased between 29% and 33% after vibration ceased. Permeability followed the same trend of decreasing with vibration and increasing after vibration, with measured values on the order of 10^(-11) m^2 to 10^(-9) m^2. It is anticipated that this poroelastic material and model will form the basis for future studies of perfused flow through human VFs, engineered VF tissues and biomaterials, and VF models.

No description available.

Previous studies have shown the importance of cricothyroid muscle activation in altering fundamental frequency in the human voice. Other studies have investigated the non-linear properties of vocal fold tissue and the impact of this non-linearity on frequency response. Several physical models of the vocal folds have been made for research purposes. However, all have been isotropic in nature with linear stress-strain properties. The purpose of this study was to create a physical model with non-linear stress-strain properties to investigate the frequency response of the model as cricothyroid muscle activation was simulated (in other words, as the vocal folds were stretched in an anterior-posterior dimension). In this study the physical models of the vocal folds were stretched in 1 mm increments and the fundamental frequency (F0) was recorded at each position. Subglottal pressure was also monitored and phonation threshold pressures were recorded for each adjustment in length and vocal fold tension, because this can influence F0. Results were obtained for models with and without non-linear properties for comparison. Tensile tests were also conducted for the linear and non-linear synthetic vocal folds. Results indicate that non-linear models demonstrated a more substantial frequency response than linear vocal fold models and a more predictable F0 increase with respect to increasing vocal fold length. Phonation threshold pressures also increased with increasing vocal fold length for non-linear vocal fold models. This trend was reversed for linear vocal fold models, with phonation threshold pressures decreasing with increasing vocal fold length. These results indicate that the non-linear vocal fold models more accurately represent the human vocal folds than do linear models. This study serves as the foundation for future research to quantify the impact of non-linear tissue properties versus active tensioning (through antagonistic thyroarytenoid muscle activation) on F0 response and phonation threshold pressure.

No description available.

The movement and control of the vocal folds within the laryngeal cavity enables three crucial physiological functions: 1) allowing respiration by opening, 2) aiding in airway protection by closing, and 3) regulating sound production during phonation. Although treatment options have improved, many of the estimated 7.5 million individuals in the United States who are annually affected by voice-related disorders still face serious challenges related to dysphonia and dysphagia. The need for improved voice-disorder treatments has motivated the work presented in this dissertation which focuses on modeling and manufacturing the vocal folds and aims to answer three main questions: 1) what are the mechanical properties of the vocal folds and how do they change across the full vocal range? 2) how do those properties influence the dynamic behavior of the tissue? and 3) can we manufacture a synthetic vocal fold model that exhibits a desired and controllable dynamic behavior? First, the elastic properties of sixteen porcine vocal folds were evaluated through uniaxial tensile tests on a custom built experimental setup. Stress-strain data was analyzed using an optimization method to yield continuous model parameters which described the linear and nonlinear elastic regions as well as transition points between those regions. Next, the impact of the vocal fold elastic properties on the frequencies of vibration was evaluated through dynamic tests on excised porcine larynges. Sound data was analyzed via a spectrogram and through the use of fast Fourier transforms to study changes in the frequency of vibration while the vocal folds were stretched. Additionally, a mathematical aeroelastic model of phonation was implemented to further evaluate the changing elastic properties on vocal fold dynamics. Next, eight synthetic vocal fold models were created, each with varying mechanical properties and a geometry based on reported anatomical measurements of porcine vocal folds. The synthetic models were then dynamically tested to further study the impact of changes in mechanical properties on the dynamic behavior of the synthetic vocal folds. / Doctor of Philosophy / The movement and control of the vocal folds within the voice-box enables three crucial physiological functions: 1) allowing respiration by opening, 2) aiding in airway protection and swallowing by closing, and 3) regulating sound production during vocalization. Although treatment options have improved, many of the estimated 7.5 million individuals in the United States who are annually affected by voice-related disorders still face serious challenges related to speech production and swallowing which often results in significant detrimental impacts to quality of life. The need for improved treatments is most easily observed in the evaluation of treatment options following a total laryngectomy, which is a procedure where the entire voice-box is removed often due to cancer. Following a laryngectomy, all three of the vital functions of the vocal folds are immediately impacted as patients adjust to breathing through and protecting a redirected airway and are forced to use alternative methods of speech production which often result in monotone or robotic-sounding speech. The need for improved voice-disorder treatments has motivated the work presented in this dissertation which focuses on modeling and manufacturing the vocal folds and aims to answer three main questions: 1) what are the mechanical properties of the vocal folds? 2) how do those properties influence the dynamic behavior of the tissue during sound production? and 3) can we manufacture synthetic vocal folds that produce a desired and controllable dynamic behavior? Sixteen porcine vocal fold samples were mechanical tested to evaluate the elastic properties of the tissue. Next, porcine voice-box samples were experimentally tested in a way that simulated sound production by subjecting the samples to a heated and humidified air flow, similar to the air flow conditions coming out of the lungs. In this way, the relationship between the tissue properties and the frequencies of sound was investigated. Lastly, the synthetic vocal fold samples were evaluated using a similar experimental protocol to further investigate the impact of changing structural properties on the dynamics of the vocal folds during sound production.

Thesis (Ph. D.)--University of Oregon, 2005. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 173-185). Also available for download via the World Wide Web; free to University of Oregon users.

Voiced communication plays a fundamental role in society. Voice research seeks to improve understanding of the fundamental physics governing voice production, with the eventual goal of improving methods to diagnose and treat voice disorders. For this thesis, three different aspects of voice production research were studied. First, porcine vocal fold medial surface geometry was determined, and the three-dimensional geometric distortion induced by freezing the larynx, especially in the region of the vocal folds, was quantified. It was found that porcine vocal folds are qualitatively geometrically similar to canine and human vocal folds, as well as commonly used models, and that freezing of tissue in the larynx causes distortion of around 5%. Second, a setup of multiple high-resolution cameras and a stereo-endoscopy system simultaneously recorded positions on the superior surface of synthetic, self-oscillating vocal fold models to estimate the error in the measurement of the three-dimensional location by the stereo-endoscopy system. The error was found to be low in the transverse plane, whereas the error was relatively large in the inferior-superior direction, suggesting that the stereo-endoscope is applicable for in vivo measurements of absolute distances of the glottis in the transverse plane such as glottal length, width, and area. Third, a function for strain-varying Poisson's ratio for silicone was developed from experimental data. It is anticipated that the findings herein can aid voice researchers as they study voice production, leading to improved voice care.

Human voice diagnosis is a complicated problem, even nowadays. The reason is poor access to the body itself and the high frequencies of vocal fold vibrations. One of the clinically available imaging methods to address these problems is Videokymography - a technology for capturing the vocal fold vibrations using a special line CCD camera. Individual lines stacked on top of each other form videokymographic recording. Videokymographic images are suitable for automatic characteristics extraction, therefore helping to reduce the laryngologist workload. For this purpose, the set of such methods is being developed in the Department of Image Processing in the Institute of Information Theory and Automation of the Academy of Science of Czech Republic. The ventricular band position and shape determination is one of the important, but difficult, tasks. The aim of this thesis is to propose new method of automatic detection of ventricular band on videokymographic recording using digital image processing techniques.