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Simulation of the sound transfer via human ear
Hájek, Petr ; Švancara, Pavel (referee) ; Pellant, Karel (advisor)
The presented thesis concerns the biomechanics of hearing. The main aim of this work is the determination of so called corrections which allow for the comparison of synthetic audiograms and measured audiograms. With these corrections we attempt to overcome the discrepancy that exists between the computational modelling and audiological measurement. The discrepancy lies in a fact that the computational modelling usually simulates the sound coming from a free eld to the external auditory canal, while audiological measurement is realized by audiological headphones, whether the auditory system is healthy or injured. Then corrections adjust the computational model so that the obtained result is comparable to audiological measurement. In this work is also addressed the influence of stapes kinematics to the excitation of basilar membrane. The movement of stapes consists of piston-like movement and rocking movement. The computational simulation shows which movement is more signicant for the excitation of basilar membrane and how this effect can be used in otosurgery, in particular, for type IV of tympanoplasty.
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Computational modelling of function of human vocal folds
Klíma, Jaromír ; Vašek, Martin (referee) ; Švancara, Pavel (advisor)
Master thesis deals with creating of the numerical model of the human vocal folds. Calculation algorithm is designed to include vocal chordsinteraction with the air flow. Analysis of the results achieved by the numerical simulations and calculations are focused on the pressure and velocity conditions in the areas under vocal folds, between vocal folds and above vocal folds. Movement and stress analysis of individual layers of vocal folds has been made. This analysis is limited only for physiological health vocal folds without pathology and disease. Modal analysis of structural and acoustic environment, backround research of vocal folds function and summary of some published overviews of numerical models is part of this work.
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Analyses of Mechanical Tasks in ADAMS
Rybár, Šimon ; Švancara, Pavel (referee) ; Hadaš, Zdeněk (advisor)
The aim of this thesis was to create parametric models of technical systems in Adams software. The simulations were made to analyze the systems from kinematic and dynamic point of view. In some cases, the simulation results were compared with the results obtained by the analytic method. The thesis is divided into three chapters. The first defines the area and aims of the thesis. The second one defines multibody system and closely presents the software and its features. The third chapter contains five different examples which demonstrate the abilities of Adams. In the conclusion, own information, overall rating and educational recommendations are summarized.
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Finite element modelling of voice propagation through the vocal tract and around the human head
Tomeček, Vojtěch ; Pellant, Karel (referee) ; Švancara, Pavel (advisor)
This diploma thesis deals with creating of finite element model for the analysis of acustic waves radiation through human vocal tract and through the head surrounding space. The thesis contains a short overview of the anatomy of relevant parts and a short overview of formerly published models relevant to the topic. Then the process of creating the 3D model of human head, including the vocal tract, based on CT scans, and the mesh itself follows. This is succeeded by the computational solution taking in the acount the acoustic absorption of the vocal tract walls and radiation into the open space. The results gained are compared to relevant literature on this topic. The changes in frequency spectra in specific nodes of the mesh are reviewed and compared to relevant literature on the topic. The results could be used as basis of eventual frequention corrections of microphones used for voice diagnosis or registration in general, eg of speach or singing.
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Computational modeling of noise emitted by tram wheel during cornering
Motyka, Jakub ; Fiedler, Robert (referee) ; Švancara, Pavel (advisor)
This thesis deals with computational modeling of curve squeal noise phenomena which occurs during cornering tight curves by trams. Lateral creep between rail and wheel and slip-stick phenomena leads to self-excited vibrations of the wheel which, therefore, emits unpleasant high-pitched noise. Two FEM models in frequency domain are carried out. First model is based on prestressed modal analysis. Due to unsymmetric stiffness matrix, unstable eigenvalues can occur. It is assumed that self-excited vibrations occurs on frequencies corresponding to that eigenvalues. Second model uses harmonic response analysis. It examines vibrations of the wheel excited by lateral creep force acting in contact region. This force is obtained externally by simple time-domain model. Results from harmonic response are used consequently for noise radiation computation.
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Computational modelling of aerodynamic noise of flow past a solid body
Sýkora, Daniel ; Hájek, Petr (referee) ; Švancara, Pavel (advisor)
Diploma thesis is focused on computational modelling of aerodynamic noise of flow past a solid body. Computation of flow around a cylinder is performed for different meshes and time steps in initial part of the thesis. Results from every computation are compared. Computation aerodynamic noise due to flow around a cylinder is simulated in other part of diploma thesis. In the second benchmark computation, turbulent models have to be considered, because flow with high Reynolds number is turbulent. Computation is based on two different ways: acoustic analogy and direct method. A few different turbulent models is described and is analyzed influence to modelling aerodynamic noise. The results and knowledge of the benchmarks computation have been used in compu-tational modelling of aerodynamic noise of flow around simplified side view mirror. Surface (2D) and spatial (3D) simulations are performed. Based on computation modelling of aerodynamic noise of flow around simplified side view mirror has been designed new geometry, that aim is reduced aerodynamic noise and improved aerodynamic parameters.
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Computational modelling of human voice propagation through the vocal tract and in space around the head
Švarc, Martin ; Pellant, Karel (referee) ; Švancara, Pavel (advisor)
The following master thesis deals with creating a computational model for acoustic wave distribution by the human vocal tract and then the space around a human head. Detailed mapping of the sound field around the human head is important for more accurate measurement of the human voice. Part of this work is the creation of three-dimensional finite element model of the human head and the vocal tract during phonation of the vowel /:a/ based on the data from the computational tomography. Further the literature search of the function of the vocal tract, biomechanics of the making of the human voice, an overview of the computational models so far published in the literature and in literature reported measurements of the distribution of the human voice by the vocal tract and then in the space around the head . The following is the actual numerical solution of the acoustic waves distribution from the vocal cords through the vocal tract and then the space around the human head when thinking of acoustic absorption on the walls of the vocal tract and on the skin of the head for different types of waking of the model. The results are compared with previously published measurements of the distribution of the human voice and mainly the distortion of the frequency spectra at each specific node in the space around the head and in its vicinity of where the sensor microphones are typically placed are analyzed. Results of the computational modeling will eventually be used for frequency correction for various positions of the microphones scanning the voice distribution in its diagnosis, speech or singing.
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Finite element modelling of pathological changes in human vocal folds tissue and their influence on videokymograph
Martínek, Tomáš ; Matug, Michal (referee) ; Švancara, Pavel (advisor)
Master´s thesis deals with creating planar computational model of human folds, involving fluid-structure interaction. With this model, the influence of changes in vocal folds tissue layers (stiffness, thickness) and their effects on the videokymograph image are studied. Analysis of the results also deals with the evaluation of pressure at selected points below, between and above the vocal folds. The results indicate a possible similarity with the behavior of human vocal folds with pathology. Background research of vocal folds function, an overview of vocal folds pathology and summary of computational models are included.
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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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