National Repository of Grey Literature 11 records found  1 - 10next  jump to record: Search took 0.02 seconds. 
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).
Numerical simulation of videokymographic images from the results of the finite element model
Švancara, P. ; Horáček, Jaromír ; Martínek, T. ; Švec, J. G.
The study presents a two-dimensional (2D) finite element (FE) model of the fluid-structure-acoustic interaction during flow induced self-oscillation of the human vocal folds. The FE model combines the FE models of the vocal folds, the trachea and the simplified human vocal tract shaped for phonation of vowel [a:]. The fluid-structure interaction is solved using explicit coupling scheme with separated solvers for structure and fluid domain. The developed FE model comprises large deformations of the vocal-fold tissue, vocal-fold contact, fluid-structure interaction, morphing the fluid mesh according to the vocal-fold motion (Arbitrary Lagrangian-Eulerian approach), solution of unsteady viscous compressible airflow described by the Navier-Stokes equations and airflow separation during the glottis closure. The effect of lamina propria thickness and material properties on simulated videokymographic (VKG) images of vocal-fold vibrations are analyzed. Such variation of the lamina propria properties can be caused by certain vocal-fold pathologies such as Reinke's edema. The developed FE model can be used to study relations among pathological changes in vocal folds tissue, the resulting VKG images and the produced sound spectra.
Measurement of vibration, flow and acoustic characteristics of a human larynx replica
Horáček, Jaromír ; Bula, Vítězslav ; Radolf, Vojtěch ; Vampola, T. ; Dušková, Miroslava
The study presents results of in vitro measurements of voicing performed on the developed artificial larynx based on the CT images of human larynx taken during phonation. The measured phonation characteristics are in good agreement with the values found in human larynges. The knowledge of these characteristics for the vocal folds replica can be useful for experimental verification of developed sophisticated 3D computational finite element models of phonation due to relatively exactly defined input material and geometrical parameters, which is problematic to obtain reliably in humans.
Finite element modelling of sound pressure around the human head during phonation
Švancara, P. ; Tomeček, V. ; Horáček, Jaromír ; Švec, J. G.
The study presents finite element (FE) model of sound propagation through the vocal tract and around the human head during speech production. Similar experimental studies are not easily realisable. The FE model of the acoustic spaces corresponding to the human vocal tract for Czech vowel [a:] and acoustic space around the human head was created from computer tomography (CT) images. Modal and transient analyses (excitation by a short pulse) are used for analysis of resonant characteristics of the FE model. The production of vowel is then simulated using transient analysis of the FE models excited by Liljencrants-Fant’s (LF) glottal signal model. Formant frequencies detected from computed spectra are in good agreement with results of modal analysis and with literature. The results of numerical simulation enable evaluating of the transfer functions between a reference point and any point in the space around the head.
Experimental investigation of air pressure, acoustic characteristics and vibrations of vocal folds on a complex physical model of phonation in humans.
Horáček, Jaromír ; Radolf, Vojtěch ; Bula, Vítězslav ; Veselý, Jan ; Laukkanen, A. M.
The contribution aims to provide material that can be used in development of more realistic physical as well as theoretical models of voice production. The experimental set-up, methodology and the results of measurement of airflow rate, subglottal, oral and generated acoustic air pressures are presented together with the simultaneously measured flow-induced vibrations of a vocal folds replica, made of soft silicon rubber, and recorded by a high speed camera. The data were measured during a ‘soft’ phonation just above the phonation onset, given by the phonation threshold airflow rate, and during a ‘normal’ phonation for the airflow rate of about three times higher. A model of the human vocal tract in the position for production of vowel [u:] was used and the flow resistance was raised by phonating into a glass resonance tube either in the air or having the other end of the tube submerged under water, and by phonating into a narrow straw. The results for the pressures presented in time and frequency domain are comparable with the physiological ranges and limits measured in humans for ordinary phonation and for production of vocal exercises used in voice therapy.
Effect of the size of piriform sinuses on the voice quality
Vampola, T. ; Horáček, Jaromír
The influence of piriform sinuses (PS) on the resonance and antiresonance characteristics of the vocal tract is investigated. The change in sizes of PS cavities alters the resulting voice quality. Pilot studies reveal that additional formants caused by PS can occur in the frequency range of 3 – 5 kHz, i.e., in the range which is important for the production of the so called singer’s or speaker’s formant. This contribution therefore aims at investigating the influence of the side cavities of the vocal tract in more detail using two computational models of the vocal tract. First, is presented analysis of the influence of the acoustic spaces of PS on the existence of resonances and antiresonances in the spectra of the acoustic signal simulated using a reduced finite element (FE) model of the human vocal tract. Then the full FE model is used for the analysis by using direct numerical simulations of phonation.
Measurement of contact stress in a self-oscillating model of human vocal folds
Horáček, Jaromír ; Bula, Vítězslav ; Veselý, Jan ; Radolf, Vojtěch
The contribution presents in vitro measurement of contact stress in the artificial vocal folds made of a silicon rubber excited by airflow with synchronous registration of the flow induced vocal fold vibrations using a high speed camera, measurement of subglottal dynamic and mean air pressure and the generated acoustic signal. The measured maximum impact stress, maximum glottal opening and sound pressure level are compared with data found in excised larynges as well as with the values numerically simulated by the aeroelastic model of vocal fold self-oscillations.
Simulation of the human vocal fold vibrations – sensitivity to the material parameters
Vampola, T. ; Horáček, Jaromír ; Klepáček, I.
A 3D finite element (FE) fully parametric model of the human larynx was developed and used for numerical simulation of vocal folds vibrations excited by a prescribed intraglottal aerodynamic pressure. The complex model consists of the arytenoid, thyroid and cricoid cartilages. The vocal fold tissue is modelled as a three layered orthotropic material and the FE contact elements are used for modelling the vocal folds collisions. The principal and shear stresses on the surface the vocal fold tissue are computed in time domain.
Experimental investigation of air pressure and acoustic characteristics of human voice. Part 1: Measurement in vivo
Horáček, Jaromír ; Radolf, Vojtěch ; Bula, Vítězslav ; Veselý, Jan ; Laukkanen, A. M.
This contribution is aimed to provide material that can be used to develop more realistic physical models of voice production. The experimental methodology and the results of measurement of subglottal, oral (substitute for subglottic) and acoustic air pressure (captured at a distance of 20 cm in front of the subject’s mouth) are presented. The data were measured during ordinary speech production and when the acoustic impedance and mean supraglottal resistance were raised by phonating into differently sized tubes in the air and having the other end submerged under water. The results presented in time and frequency domain show the physiological ranges and limits of the measured pressures in humans for normal and extreme phonation.
Influence of geometric configurations of the human vocal tract on the voice production
Vampola, T. ; Horáček, Jaromír
The three-dimensional (3D) finite element (FE) model of the human vocal tract was constructed, based on CT measurements of a subject phonating on [a:]. A special attention is given to the higher frequency range (above 3.5 Hz) where transversal modes exist between piriform sinuses (PS) and valleculae (VA) and where the higher formants can create a formant cluster known as the speaker’s or singer’s formant. Since the human ear is most sensitive to frequencies between 2 and 4 kHz concentration of sound energy in this frequency region (F4-F5) is effective for communication.

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