The study investigates differences between three most widely used methods in voice training and therapy: Phonation into a resonance tube with the outer end in the air or submerged 2-10 cm in water (‘water resistance therapy‘ with bubbling effect), and phonation into a very thin straw. One female speech trainer served as subejct. Acoustic and electroglottographic (EGG) signals, and both mean and dynamic air pressures in the mouth cavity were registered for repetitions of [pu:pu], and for phonation into the tubes, while the outer end was randomly shuttered in order to get an estimate of subglottic pressure. Soft and normal phonations were recorded. Phonation threshold decreased with tube in air, suggesting that increased input reactance assists small amplitude oscillation of the vocal folds. Oral pressure (Poral) increased with increasing impedance offered by the tube and straw, most when the tube was 10 cm in water. In most cases subglottic pressure (Psub) increased relatively more than Poral, so that tranglottic pressure (Ptrans) was higher in the exercises compared to vowel. Contact quotient (CQ) from EGG increased, which may be due to increased Ptrans. In tube 10 cm in water Ptrans decreased and CQ increased suggesting increased adduction as compensation. Exercises that increase oral eir-pressure offer a possibility to train flottal and respiratory adjustments under the influence of increased flow resistance which may prevent excessively strong vocal fold collisions. and Obsahuje seznam literatury
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 ‘soft‘ phonation onset, given by the phonation threshold airflow rate, and during ‘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 straws. 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. and Obsahuje seznam literatury
The effect of tonsillectomy on production of Czech vowels /a/ and /i/ is numerically examined. Similar experimental studies are difficult to realise on living subjects. Finite element (FE) models of the acoustic spaces corresponding to the human vocal tract for the Czech vowels /a/ and /i/ with acoustic space around the human head are used in numerical simulations of phonation. The acoustic resonant characteristics of the FE models are studied by modal and transient analyses. The production of vowels is simulated in time-domain using transient analysis of FE models excited at the position of vocal folds by analytically desctibed Liljencrants-Fant‘s (LF) glottal signal model. The results show that tonsillectomy causes frequency shifts of some formant frequencies up to 150 Hz. The frequency shift of formants significantly depends on position and size of the tonsils. and Obsahuje seznam literatury
The subject of the paper is the numerical simulation of the interaction of two-dimensional incompressible viscous flow and a vibrating airfoil inserted in a channel (e.g. wind tunnel). A solid airfoil with two degrees of freedom can rotate around the elastic axis and oscillate in the vertical direction. The numerical simulation consists of the finite element soluton of the Navier-Stokes equations coupled with the system of ordinary differential equations describing the airfoil motion. The time dependent computational domain and a moving grid are taken into account with the aid of the Arbitrary Lagrangian-Eulerian (ALE) formulation of the Navier-Stokes equations. High Reynolds numbers up to 106 require the application of a suitable stabilization of the finite element discretization. Numerical results are compared with an experiment. and Obsahuje seznam literatury
This study deals with the numerical solution of a 2D unsteady flow of a compressible viscous fluid in a channel for low inlet airflow velocity. The unsteadiness of the flow is caused by a prescribed periodic motion of a part of the channel wall with large amplitudes, nearly closing the channel during oscillations. The channel is a simplified model of the glottal space in the human vocal tract and the flow can represent a model of airflow coming from the trachea, through the glottal region with periodically vibrating vocal folds to the human vocal tract.
The flow is described by the system of Navier-Stokes equations for laminar flows. The numerical solution is implemented using the finite volume method (FVM) and the predictor-corrector MacCormack scheme with Jameson artificial viscosity using a grid of quadrilateral cells. Due to the motion of the grid, the basic system of conservation laws is considered in the Arbitary Lagrangian-Eulerian (ALE) form.
The authors present the numerical simulations of flow fields in the channel acquired from a program developed exclusively for this purpose. The numerical results for unsteady flows in the channel are presented for inlet Mach number M∞ = 0.012, Reynolds number Re∞ = 5x103 and the wall motion frequency 100 Hz. and Obsahuje seznam literatury
We show that dynamical systems in inverse problems are sometimes foliated if the embedding dimension is greater than the dimension of the manifold on which the system resides. Under this condition, we end up reaching different leaves of the foliation if we start from different initial conditions. For some of these cases we have found a method by which we can asymptotically guide the system to a specific leaf even if we start from an initial condition which corresponds to some other leaf. We demonstrate the method by two examples. In the chosen cases of the harmonic oscillator and Duffing's oscillator we find an alternative set of equations which represent a collapsed foliation, such that no matter what initial conditions we choose, the system would asymptotically reach the same desired sub-manifold of the original system. This process can lead to cases for which a system begins in a chaotic region, but is guided to a periodic region and vice versa. It may also happen that we could move from an orbitThe paper deals with numerical simulation of a compressible flow in time-dependent 2D domains with a special interest in medical applications to airflow in the human vocal tract. The mathematical model of this process is described by the compressible Navier-Stokes equations. For the treatment of the time-dependent domain, the arbitrary Lagrangian-Eulerian (ALE) method is used. The discontinuous Galerkin finite element method (DGFEM) is used for the space semidiscretization of the governing equations in the ALE formulation. The time discretization is carried out with the aid of a linearized semi-implicit method with good stability properties. We present some computational results for the flow in a channel, representing a model of glottis and a part of the vocal tract, with a prescribed motion of the channel walls at the position of vocal folds. of one period to an orbit of another period.
This paper describes the free transverse vibration analysis of a thin circular plate, subjected to in plane stretching, whilst in interaction with a cylindrical acoustic cavity. An analysis is performed which combines the equations describing the plate and the acoustic cavity to form a matrix equation which, when solved, produces the natural frequencies (latent roots) of the coupled system and associated latent vectors which describe the mode shape coefficients of the plate. After assessing the numerical convergence of the method, results are compared with those from a commercial finite element code (ANSYS). The results analysis is then extended to investigate the effect of stressing upon the free vibration of the coupled system. and Obsahuje seznam literatury