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Analysis of Modal Shapes and Natural Frequencies of Real-Shaped Vocal Fold
Horčic, Václav ; Švancara, Pavel (referee) ; Hájek, Petr (advisor)
This bachelor's thesis deals with the modal analysis of a model based on a 3D scan of the human vocal cords. This is a model solved by the finite element method, where the value of the first natural frequency roughly corresponds to the value of the fundamental frequency of female vocal folds. The research part of the thesis is devoted to an overview of finite element models of the geometry of the vocal cords, which is followed by a brief description of the anatomy and physiology of the human speech system together with the theory of the formation of the human voice. The finite element model is created using a 3D scan of the vocal folds in the commercial program ANSYS Workbench, in which it is solved by the finite element method.
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Using of Transfer Matrix Method for Modal Characteristics of Vocal Tract
Meisner, Patrik ; Švancara, Pavel (referee) ; Hájek, Petr (advisor)
The first part of the bachelor thesis describes anatomy of the vocal tract, voice creation and its modification. Some pathologies are listed at the end of the first part. The contents of second part are previously published computational models of the vocal tract followed by the method of transfer matrices for the Czech vowel [u:]. Modal analysis is performed by the transfer matrix method. The output are first three natural frequencies. Obtained frequencies are compared to values in the literature and to values calculated by the finite element method.
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Compensatory Vocal Folds for Source Voice Generation: Computational Modeling of Vocal Folds Function
Matug, Michal ; Vampola, Tomáš (referee) ; Horáček, Jaromír (referee) ; Švancara, Pavel (advisor)
This doctoral thesis focuses on computational modelling of human vocal folds and vocal tract functions using finite element method (FEM). Human voice is crucial in human communication. Therefore one of the main targets of current medicine is creation of artificial vocal folds, which would substitute the original vocal folds. The computational modelling can be used to understand principles of voice production, determination of parameters that the artificial vocal folds have to meet and verification of their functionality. First part of this thesis focuses on modelling of human voice creation by whisper. Influence of intraglottal gap on eigenvalues distribution for individual vowels was analysed using FEM vocal tract and trachea model. Further there is presented two-dimensional (2D) finite element model of the flow-induced self-oscillation of the human vocal folds in interaction with acoustic spaces of the vocal tract. The 2D vocal tract model was created on the basis of converting the data from magnetic resonance images (MRI). Explicit coupling scheme with separated solvers for structure and fluid domain was used for modelling of the fluid-structure interaction. Created computational model comprises: large deformations of the vocal folds tissue, contact between vocal folds, fluid-structure interaction, morphing the fluid mesh according to the vocal-fold motion (Arbitrary Lagrangian-Eulerian approach), unsteady viscous compressible or incompressible airflow described by the Navier-Stokes equations and airflow separation during glottis closure. This model is used to analyse the influence of stiffness and damping changes in individual vocal fold tissue layers (in particular in superficial lamina propria). Part of this computational analysis is also comparison of vocal folds behaviour for compressible and incompressible flow model. Videokymograms (VKG) are subsequently created from obtained results of FEM calculations which enable to compare individual variants between themselves and with motion of real human vocal folds. In next part of this thesis is presented three-dimensional (3D) finite element model of the flow-induced self-oscillation of the human vocal folds. This 3D model was created from a previous 2D model by extrude to the third direction. Using this model was again compared influence of compressible and incompressible flow model on vocal folds motion and generated sound by using videokymograms and acoustic spectra. The last part of this thesis focuses on the possibility to replace missing natural source voice in form reed-based element. Behaviour of reed-based element was analysed using computational modelling and using measurements on experimental physical model. The physical model enables changes in setting gap between reed and reed stop and performing acoustical and optical measurements.
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Using of Transfer Matrix Method for Modal Characteristics of Vocal Tract
Meisner, Patrik ; Švancara, Pavel (referee) ; Hájek, Petr (advisor)
The first part of the bachelor thesis describes anatomy of the vocal tract, voice creation and its modification. Some pathologies are listed at the end of the first part. The contents of second part are previously published computational models of the vocal tract followed by the method of transfer matrices for the Czech vowel [u:]. Modal analysis is performed by the transfer matrix method. The output are first three natural frequencies. Obtained frequencies are compared to values in the literature and to values calculated by the finite element method.
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Using the proper orthogonal decomposition analysis for detecting pathologic vocal fold vibration
Štorkán, J. ; Vampola, T. ; Horáček, Jaromír
A three-dimensional (3D) finite element (FE) fully parametric model of the human larynx based on computer tomography (CT) measurements was developed and specially adapted for numerical simulation of vocal folds vibrations with collisions. The complex model consists of the vocal folds, arytenoids, thyroid and cricoid cartilages. The vocal fold tissue is modeled as a four layered material where part of the cover was substituted by a liquid layer modelling the superficial layer of lamina propria. The proper orthogonal decomposition (POD) analysis of the excited modes of vibration was used for detecting changes in vibration properties of the vocal folds caused by pathologic changes of vocal fold structure (vocal nodule).
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Compensatory Vocal Folds for Source Voice Generation: Computational Modeling of Vocal Folds Function
Matug, Michal ; Vampola, Tomáš (referee) ; Horáček, Jaromír (referee) ; Švancara, Pavel (advisor)
This doctoral thesis focuses on computational modelling of human vocal folds and vocal tract functions using finite element method (FEM). Human voice is crucial in human communication. Therefore one of the main targets of current medicine is creation of artificial vocal folds, which would substitute the original vocal folds. The computational modelling can be used to understand principles of voice production, determination of parameters that the artificial vocal folds have to meet and verification of their functionality. First part of this thesis focuses on modelling of human voice creation by whisper. Influence of intraglottal gap on eigenvalues distribution for individual vowels was analysed using FEM vocal tract and trachea model. Further there is presented two-dimensional (2D) finite element model of the flow-induced self-oscillation of the human vocal folds in interaction with acoustic spaces of the vocal tract. The 2D vocal tract model was created on the basis of converting the data from magnetic resonance images (MRI). Explicit coupling scheme with separated solvers for structure and fluid domain was used for modelling of the fluid-structure interaction. Created computational model comprises: large deformations of the vocal folds tissue, contact between vocal folds, fluid-structure interaction, morphing the fluid mesh according to the vocal-fold motion (Arbitrary Lagrangian-Eulerian approach), unsteady viscous compressible or incompressible airflow described by the Navier-Stokes equations and airflow separation during glottis closure. This model is used to analyse the influence of stiffness and damping changes in individual vocal fold tissue layers (in particular in superficial lamina propria). Part of this computational analysis is also comparison of vocal folds behaviour for compressible and incompressible flow model. Videokymograms (VKG) are subsequently created from obtained results of FEM calculations which enable to compare individual variants between themselves and with motion of real human vocal folds. In next part of this thesis is presented three-dimensional (3D) finite element model of the flow-induced self-oscillation of the human vocal folds. This 3D model was created from a previous 2D model by extrude to the third direction. Using this model was again compared influence of compressible and incompressible flow model on vocal folds motion and generated sound by using videokymograms and acoustic spectra. The last part of this thesis focuses on the possibility to replace missing natural source voice in form reed-based element. Behaviour of reed-based element was analysed using computational modelling and using measurements on experimental physical model. The physical model enables changes in setting gap between reed and reed stop and performing acoustical and optical measurements.
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Numerical simulation of video-kymographic records of the vocal fold vibration
Vampola, T. ; Horáček, Jaromír
The reconstruction of the video-kymographic records from the numerical simulation of the vocal fold vibration is used for prediction of the type of vocal fold damaged. Three-dimensional (3D) finite element (FE) fully parametric model of the human larynx was developed and used for numerical simulation of stresses during vibrating vocal folds with collisions. The complex model consists of the vocal folds, arytenoids, thyroid and cricoid cartilages. The vocal fold tissue is modeled as a three layered transversal isotropic material. The results of numerical simulation of the vocal folds oscillations excited by a prescribed intraglottal aerodynamic pressure are presented. The FE contact elements are used for modelling the vocal folds collisions and the stresses in the vocal fold tissue are computed in time domain. The damaged of the ligament tissue is simulated by the modification of the modulus of elasticity. The video-kymographic records are reconstructed for health and damaged vocal folds. The results show significant dynamic stresses in all there directions (horizontal, vertical and anterior-posterior).
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