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Computational modelling of voice propagation around the human head using finite element method
Ryšavý, Antonín ; Hájek, Petr (referee) ; Švancara, Pavel (advisor)
In the first part of this master's thesis there is briefly presented the biomechanics of the human voice creation and an overview of the hitherto published computational models of the vocal tract and dissemination of the acoustic waves around the human head. The second part of the thesis deals with the creation of the computational model of a dissemination of the acoustic waves through vocal tract and further into a space around the head during the pronouncing of the Czech vowel /a:/. The vocal tract is excited by a harmonic signal in the place of vocal chords. On the surface of the vocal tract and the part of the head including hair and skin there is defined an acoustic absorption. The dissemination of the acoustic waves in the vocal tract, in the near field around the mouth, in the area around the head and in the points on the cheeks is detailed mapped. The dissemination of the acoustic waves is analyzed in the points where the speech microphones are placed. Acoustic pressure dependence on frequency, transmission functions between defined points and the acoustic pressure amplitudes depending on the distance from the mouth are obtained. In particular, the frequency distortion of the spectra is observed at the points indicated. Furthermore, the radiation impedance in the mouth area is evaluated. The results obtained are compared with the results of the hitherto published experimental measurements and can be used for the exact measurement of human voice or for the frequency correction of the microphones during the scann of the speech and sing placced in the analyzed points.
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Computational modelling of high-frequency noise inside cabin of aircraft EV-55M
Straka, Martin ; Pellant, Karel (referee) ; Švancara, Pavel (advisor)
This thesis describes methods of high frequency noise and vibrations computation of cabin part of EV–55M (aircraft developed by Evektor Kunovice). There is a brief summary of methods used for determining high frequency noise and vibrations in the first part of the thesis. Detailed explanation is given for Statistical Energy Analysis (SEA) which is nowadays the most dominant method in this area. The energy balance equation is derived in this chapter and SEA parameters such as modal density, damping loss factor, coupling loss factor and power input are introduced here. Next part deals with main noise sources of propeller driven and jet aircraft and passive and active noise controls are discussed. Practical part of this thesis deals with modeling aircraft EV–55M fuselage using VA One SEA module. Two models were created. First of them is only an outside fuselage with aircraft flooring and the second one is extended by interior trim panels and is applicable for simulation of noise control treatments. Computational modeling is accompanied by experimental measurement of passive noise control material characteristics. Postprocessing of information obtained from impedance tube measurement was performed in FOAM – X. Determined characteristics of porous material were used as inputs to VA One and reduction of sound pressure level in fuselage cavities by using noise control treatment was found. In conclusion there is a summary of noise transmission paths from sources to interior cavity and some treatments of them are simulated
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Computational modelling of interaction between oscillating vocal folds and air flow
Pavlica, Ondřej ; Matug, Michal (referee) ; Švancara, Pavel (advisor)
Master thesis deals with creating numerical model of the human vocal folds. Calculation algorithm includes interaction between vocal chords and the air flow. Modal analysis of structural and acoustic environment, backround research of vocal folds function and summary of some published overviews of numerical models are parts of this work. 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. Impact of tissue thickness on resulting behaviour has been assessed.
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Utilization of carbon fibre for construction of elastic elements of mountain bike rear triangle
Linda, Jakub ; Švancara, Pavel (referee) ; Březina, Lukáš (advisor)
The aim of the thesis is to design a carbon elastic element in the suspension mechanism of the rear wheel of a mountain bike. The elastic element will replace the rotary link and its deformation will allow movement of the rear wheel suspension mechanism. At the beginning, the thesis deals with the theoretical introduction to bicycle geometry, types of rear wheel suspension mechanisms and their characteristics. Later on, the work is devoted to composite materials in general, and it also deals with methods of manufacturing a composite bicycle frame and deals with the mechanics of composites. Further, the thesis is focused on the research of already existing frames utilizing the flexible element in the suspension mechanism of the rear wheel. Finally, the work focuses on the design of a full-suspension bicycle using a flexible element, justifies the choice of the replaced suspension mechanism and also justifies the individual simplifying assumptions and their impact on the solution. The elastic element is analyzed for deformations and stresses in the Ansys software. Finally, the results of the analysis and recommendations are presented.
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Analysis of Formant Areas During Sung Vowels
Kukosa, František ; Švancara, Pavel (referee) ; Jirásek, Ondřej (advisor)
The study analyzes the formant zones of male voices in singing vowels with main focus on opera, chest and head vocal registers. The results of this work are based on the recordings of five singers, taken in an anechoic chamber. For the analysis of these recordings in the frequency domain were used the FFT algorithm and the LPC analysis. The results describe the nature of the individual registers and show the importance of the singing formants for singers. Especially for opera vocal register where the vocal formants, along with a natural vibrato technique, are very important.
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Application of Fluid-structure Interaction on Oscillating Human Vocal Folds
Meisner, Patrik ; Švancara, Pavel (referee) ; Hájek, Petr (advisor)
The presented thesis is involved in the biomechanics of phonation. The aim of the thesis is to set a fluid-structure interaction between the vocal folds and air flow when the pressure from lungs reaches the physiological values. In the expected outcome the self-oscillating vocal folds should be observable with characteristics shape-shift from convergent to divergent. In theory part of the thesis is described Anatomy of the vocal tract, physiology of the human phonation, research of computational simulations, experiments and visualisation methods are described in the theory part of the thesis. In the second part, setup of computational simulation with the finite element method is presented. Besides of the fluid-structure interaction the acoustical model is set. Achieved results are presented and compared to the results in literature. Displacements are evaluated from the structural model and pressures, velocities and flow velocities are evaluated from fluid model, so as acoustics results.
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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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