Models and Analysis of Vocal Emissions for Biomedical Applications

The International Workshop on Models and Analysis of Vocal Emissions for Biomedical Applications (MAVEBA) came into being in 1999 from the particularly felt need of sharing know-how, objectives and results between areas that until then seemed quite distinct such as bioengineering, medicine and singing. MAVEBA deals with all aspects concerning the study of the human voice with applications ranging from the neonate to the adult and elderly. Over the years the initial issues have grown and spread also in other aspects of research such as occupational voice disorders, neurology, rehabilitation, image and video analysis. MAVEBA takes place every two years always in Firenze, Italy

Modelling Physical Mechanisms of Nodule Development in Phonotraumatic Vocal Hyperfunction using Computational Vocal Fold Models

Vocal hyperfunction is a prevalent voice disorder with significant impacts on the daily lives of patients, but has poorly understood causes. At its root, vocal hyperfunction is neurological, involving excessive muscular activation due to compensation for some underlying issue. In order to improve understanding of the causes of this disorder and ultimately improve its treatment, this thesis uses computational models to investigate mechanical aspects in the development of vocal fold nodules in phonotraumatic vocal hyperfunction (a specific class of vocal hyperfunction), specifically: whether biomechanical differences in stiffness of the vocal folds can lead to inefficient speech production that predisposes one to developing these nodule, and whether swelling can establish an amplifying feedback loop, a so-called "vicious cycle", wherein swelling leads to compensatory adjustments that incur further swelling and ultimately lead to nodule. To address these questions a two-dimensional finite-element vocal fold model coupled with a simplified one-dimensional flow model was developed with modifications to this basic model made to study the phenomena of interest. Towards modelling swelling, a computationally efficient approach to model the epithelium layer of the vocal folds is also developed and validated. To investigate the first research question, the aforementioned model was adapted to study phonation onset pressure, a measure of effort required to produce speech, as a function of vocal fold stiffness. The results show that onset pressure is primarily dependent on just three stiffness distributions: smooth distributions with body-cover stiffness differences and smooth distributions with inferior-superior stiffness differences minimize onset pressure while a uniform stiffness increase increases onset pressure. Since a uniform stiffness increase increases the natural frequency of the vocal folds, this increase in onset pressure is roughly associated with increases in frequency. This suggests that for a given average stiffness (onset frequency) deviations from an optimal body-cover and inferior-superior-like distribution lead to increases in phonatory effort that could increase susceptibility to vocal hyperfunction. To investigate the second research question, the finite element model was augmented with a model of swelling, as well as an epithelium using a membrane model. Results showed that swelling has negligible impact on loudness of speech but significantly influences frequency, and that furthermore, swelling increases measures of phonotrauma. These results suggest that swelling could incur a vicious cycle. Specifically, a decrease in fundamental frequency initiates compensatory adjustments through increased muscle tension and subglottal pressure, which tends to increase phonotrauma in the folds, and increased swelling with phonotrauma does not tend to limit further swelling. This result demonstrates how swelling can potentially lead to the formation of nodule

Models and Analysis of Vocal Emissions for Biomedical Applications

The Models and Analysis of Vocal Emissions with Biomedical Applications (MAVEBA) workshop came into being in 1999 from the particularly felt need of sharing know-how, objectives and results between areas that until then seemed quite distinct such as bioengineering, medicine and singing. MAVEBA deals with all aspects concerning the study of the human voice with applications ranging from the neonate to the adult and elderly. Over the years the initial issues have grown and spread also in other aspects of research such as occupational voice disorders, neurology, rehabilitation, image and video analysis. MAVEBA takes place every two years always in Firenze, Italy

Numerical Modeling of Vocal Control and Patient-specific Surgical Planning of Type 1 Thyroplasty

This study aims to develop knowledge about the roles of intrinsic laryngeal muscles on voice control in both healthy and disordered conditions through comprehensive computational models. The phonation simulator was built by combining a three-dimensional high-fidelity MRI-based model of the larynx, active muscle mechanics, and fluid-structure-acoustic interaction model, which enabled the exploration of the underlayer mechanisms of the link between individual and/or group muscles contractions under both symmetric and asymmetric activations, vocal fold posture, vocal fold vibration, and voice outcomes during voice production. The first part of this research extensively investigated the effects of cricothyroid and thyroarytenoid muscle activations on voice characteristics through a parametric study. The role of these intrinsic muscles in the adjustment of geometrical and mechanical properties of vocal fold pre-phonatory posture, glottic flow aerodynamics, and acoustic and how all these components interact were explored. Results were comprehensively validated, and the link between elements of phonation was described in detail. In the next step, due to the model\u27s ability in the individual muscle activations, unilateral vocal fold paralysis was simulated, and the characteristics of disordered voice were analyzed. The voice simulator was then combined with the implant insertion model and genetic algorithm method to build a computational framework for patient-specific surgical planning of type 1 thyroplasty. This surgery is a standard procedure for treating unilateral vocal fold paralysis; however, it is subject to challenges mainly due to the small size of the implant and the high sensitivity of the voice outcome to the implant shape and position. Therefore, although the patient\u27s voice could be improved, the results might not be as satisfying as expected. Despite actual surgery, with very little room for try and error, the ideal implant could be achieved by optimizing the implant based on the patient\u27s desired voice using the presented computational framework. Both healthy and diseased cases and the corrected case using the optimized implant were simulated. Results revealed that the optimized implant could restore the aerodynamic and acoustic features of the disordered voice in producing a sustained vowel utterance. Furthermore, the performance of the implant in the pitch gliding test, which was simulated using temporal activation of the cricothyroid and thyroarytenoid muscles based on the first part of the study, was evaluated. In the final step, a physics-informed neural network-based algorithm was presented to reconstruct the three-dimensional cyclic vibration of vocal fold using two-dimensional sparse experimental data and laws of physics. Key acoustic parameters and vibratory dynamics of vocal folds and other parameters, such as flow rate, pressure distribution, and contact force, which are difficult to measure experimentally, were successfully predicted

Models and Analysis of Vocal Emissions for Biomedical Applications

The International Workshop on Models and Analysis of Vocal Emissions for Biomedical Applications (MAVEBA) came into being in 1999 from the particularly felt need of sharing know-how, objectives and results between areas that until then seemed quite distinct such as bioengineering, medicine and singing. MAVEBA deals with all aspects concerning the study of the human voice with applications ranging from the newborn to the adult and elderly. Over the years the initial issues have grown and spread also in other fields of research such as occupational voice disorders, neurology, rehabilitation, image and video analysis. MAVEBA takes place every two years in Firenze, Italy. This edition celebrates twenty-two years of uninterrupted and successful research in the field of voice analysis

Models and Analysis of Vocal Emissions for Biomedical Applications

The International Workshop on Models and Analysis of Vocal Emissions for Biomedical Applications (MAVEBA) came into being in 1999 from the particularly felt need of sharing know-how, objectives and results between areas that until then seemed quite distinct such as bioengineering, medicine and singing. MAVEBA deals with all aspects concerning the study of the human voice with applications ranging from the neonate to the adult and elderly. Over the years the initial issues have grown and spread also in other aspects of research such as occupational voice disorders, neurology, rehabilitation, image and video analysis. MAVEBA takes place every two years always in Firenze, Italy. This edition celebrates twenty years of uninterrupted and succesfully research in the field of voice analysis

Models and Analysis of Vocal Emissions for Biomedical Applications

The MAVEBA Workshop proceedings, held on a biannual basis, collect the scientific papers presented both as oral and poster contributions, during the conference. The main subjects are: development of theoretical and mechanical models as an aid to the study of main phonatory dysfunctions, as well as the biomedical engineering methods for the analysis of voice signals and images, as a support to clinical diagnosis and classification of vocal pathologies

Computational modelling of mucosal wave propagation in human vocal folds

Cílem práce je na modelu hlasivky provést analýzu vlivu materiálových parametrů jednotlivých vrstev tkáně hlasivek na šíření slizniční vlny. Nejdříve je na základě literatury uveden stručný přehled současných přístupů při experimentálním a výpočtovém modelování šíření slizniční vlny. Dále je pak pomocí modální analýzy zkoumán vliv modulu pružnosti v tahu epitelu a povrchové laminy proprii na vlastní frekvence a tvary kmitů. Šíření slizniční vlny bylo následně analyzováno pomocí přechodové analýzy jako odezva hlasivky na rázové buzení silou na spodní část hlasivky. Byl vyhodnocován vliv materiálových parametrů na amplitudu a rychlost šíření slizniční vlny po povrchu hlasivky. V závěru práce je uvedeno doporučení, dle zaznamenaných výsledků, použít nižší moduly pružnosti v tahu povrchové laminy proprii v modelech s interakcí s proudem vzduchu, protože je zde mnohem výraznější šíření slizniční vlny odpovídající chování skutečných lidských hlasivek.The aim of this thesis is to analyze the influence of material parameters of individual layers of vocal cord tissue on the propagation of mucosal waves on the vocal cord model. First, a brief overview of current approaches in experimental and computational modeling of mucosal wave propagation is given on the basis of the literature. Furthermore, the influence of the modulus of elasticity in the tensile epithelium and the surface lamina of propria on the natural frequencies and shapes of oscillations is investigated by means of modal analysis. Mucosal wave propagation was then analyzed using transient analysis in response to the vocal cords to shock excitation by force on the lower part of the vocal cords. The influence of material parameters on the amplitude and speed of mucosal wave propagation over the vocal cord surface was evaluated. In the end of this thesis, the recommendation is given, according to the recorded results, to use lower modulus of elasticity in tension of the surface lamina propria in models with interaction with air flow, because there is much more pronounced mucosal wave propagation corresponding to the behavior of real human vocal cords.

Direct numerical simulation of human phonation

The generation and propagation of the human voice is studied using direct numerical simulation. A full body domain is employed for the purpose of directly computing the sound in the region past the speaker's mouth. The air in the vocal tract is modeled as a compressible and viscous fluid interacting with the vocal folds (VFs). The vocal fold tissue material properties are multi-layered, with varying stiffness, and a finite-strain model is utilized and implemented in a quadratic finite element code. The fluid-solid domains are coupled through a boundary-fitted interface and utilize a Poisson equation-based mesh deformation method. The domain includes an anatomically relevant vocal tract geometry, either in two dimensions or in three dimensions. Adult and two-year-old child anatomy inspired simulations are performed. Phonation simulations using a non-linear hyper elastic, linear elastic and viscoelastic models of the VFs are performed and compared. The sensitivity of phonation to the VF Poisson's ratio is also evaluated. Simulations are employed to investigate voice disorders related to vocal fold stiffness asymmetry and unilateral vocal fold paralysis (UVFP). Additionally, an analysis is performed for medialization laryngoplasty, a well known surgical treatment for UVFP. Phonation onset is determined from all the simulations as a measure of degree of voice disorder with phonation threshold pressure (PTP) as a key parameter for the quantification. The computational model developed is demonstrated to be consistent with prior measurements and sufficiently sensitive to be used in future studies involving VF pathologies, surgical procedures to restore voice, and/or closed loop models of voice, speech and perception.Ope

Theoretical and Numerical Analyses of Laryngeal Biomechanics: Towards Understanding Vocal Hyperfunction

Speech is a cornerstone in human communication and an irreplaceable tool for several academic, legal, and artistic careers. Producing intelligible speech is an extremely complex process, involving coupling between the air flow driven by the pressure built up in the lungs, the vibrating viscoelastic tissues in the larynx, namely the vocal folds, and the subglottal and supraglottal (vocal) tracts, including the nasal and oral passages. Therefore, the occurrence of a pathology in one of the organs responsible for voice production may result in deteriorated speech production and, consequently, a negative impact on the daily life and/or professional career of the individual. A specific class of voice disorders that is common among adults is vocal hyperfunction, which is associated with the misuse of vocal organs, resulting in inefficient voice production and, in some cases, vocal trauma. Researchers over the years have conducted clinical and numerical analyses of vocal hyperfunction and have developed assessment tools and therapeutic procedures for vocal hyperfunction; however, a comprehensive understanding of the underlying mechanisms of vocal hyperfunction remains unachieved. Fortunately, easily collected clinical measurements shed some light on potential mechanisms underlying vocal hyperfunction, and numerical and theoretical modelling campaigns of laryngeal biomechanics have shown some success in partially elucidating the biomechanics of voice production. Therefore, a potential route to pursue for a better understanding of the mechanics of vocal hyperfunction lays behind numerical and theoretical analyses guided by available clinical and experimental data. The aim of this thesis is to explore and elucidate, through four research projects, some of the underlying mechanisms associated with voice production in general and vocal hyperfunction in particular, where we resort to 1) data collected using some promising assessment tools and standard clinical measurements, and 2) models of voice production and larynx biomechanics, where theoretical and numerical analyses are conducted guided by the aforementioned clinical measurements. The first project analyses theoretically and numerically the underlying laryngeal factors altering fundamental frequency, for both healthy speakers and speakers with phonotraumatic vocal hyperfunction, during phonation offset, where clinical data of relative fundamental frequency are resorted to in modeling and analysis. We show that the clinically observed drop in fundamental frequency during phonation offset is potentially due to the decline in vocal fold collision forces, which is induced by increasing the glottal gap. We also show how the fundamental frequency drop rate can be modulated by the activation of certain laryngeal muscles, which we speculate to underlie the differences between healthy and hyperfunctional speakers. Besides, we illustrate how certain manifestations of vocal hyperfunction can also affect the drop rate during phonation offset. The second project extends the first one, where phonation onset is explored with similar numerical and theoretical approaches. We illustrate that, when all laryngeal and aerodynamic parameters are fixed in time, fundamental frequency tends to rise due to the increased vocal fold collision levels, and that matches with the clinical observations of the onset of initial or isolated vowels and, in some cases, vowels preceded by voiced consonants. On the other hand, we show through numerical simulations that the decline in fundamental frequency in the case of onset of vowels preceded by voiceless consonants requires involvement of laryngeal muscles, which we speculate to manifest the differences between healthy speakers and patients with vocal hyperfunction. In the third project, we attempt to elucidate the influence of extrinsic laryngeal muscles on posturing mechanics and phonation, and link findings with clinical observations collected from patients with vocal hyperfunction. We show how the vocal fold tension and phonation fundamental frequency vary with varying the magnitude, direction, and location of the net pulling force exerted by the extrinsic laryngeal muscles. Using the previous analysis in combination with clinical data, we pinpoint potential roles of specific extrinsic muscles in modulating fundamental frequency and we suggest some potential roles for extrinsic laryngeal muscles in hyperfunctional phonation. Finally, in the fourth project, we study the mechanics underlying curved and incomplete glottal closure configurations that are observed in some patients with vocal hyperfunction, where we develop and analyse a composite beam model for the vocal folds and we integrate it with a posturing model to enable exploring the effects of certain laryngeal maneuvers. The model predictive capability is adequate, matching clinical observations and simulations produced by high-fidelity models, yet providing useful insights into the underlying mechanism of curved glottal configurations due to its relative simplicity. Our analyses, based on the proposed model, show that the vocal fold layered structure and its interaction with the mechanical loading, resulting during laryngeal maneuvers, induce bending moments that result in different curved (convex and concave) vocal fold shapes that are associated with incomplete glottal closure patterns. We suggest, based on the conducted analyses, some potential laryngeal mechanisms that may be at play in patients with vocal hyperfunction