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Acoustic resonance characteristics of the human vocal tract with respect to a soft tissue
Radolf, Vojtěch ; Horáček, Jaromír
A mathematical model, which can help to clarify physical background of an influence of the soft tissue of vocal cavities on the formant frequencies, has been extended. Strong acoustic-structural interaction is demonstrated on the vocal tract cavity for vowel /u:/ prolonged by a tube that is used for voice training and therapy purposes. The glottis is closed by a yielding wall, considering a mass, compliance and structural damping. Viscous losses of the acoustic cavities and radiation impedance at the output are assumed. Significant change in the first acoustic resonance frequency caused by the compliance of the soft tissue at the glottis corresponds to the data found experimentally in earlier study.
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Acoustic-structural interaction in human vocal tract prolonged by a tube
Radolf, Vojtěch ; Horáček, Jaromír
Phonation into tubes is often used for voice training and therapy. This paper introduces a mathematical model, which can help to clarify physical background of an influence of the soft tissues of vocal cavities on the acoustic resonances (formant frequencies). Substantial change in the first formant frequency caused by the soft tissues in the human vocal tract is in principle in the acoustic-structural interaction of the acoustic cavity semiocluded by the tube, with the yielding wall created for example by the soft tissues in the larynx.
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Air-pressure characteristics and visualization of bubbling effect in water resistance therapy
Radolf, Vojtěch ; Horáček, Jaromír ; Bula, Vítězslav ; Laukkanen, A. M.
This study investigates the influence of a widely used method in voice training and therapy, phonation into a resonance tube with the outer end submerged in water (‘water resistance therapy’ with bubbling effect). Acoustic and electroglottographic (EGG) signals and air pressures in the mouth cavity were registered and the formation of bubbles was studied using high speed camera. Bubbling frequency dominates in the spectra of the pressure signal being about 15 dB higher than the amplitude of the first harmonic, which reflects the fundamental frequency of the vocal folds’ vibration. Separation of the bubbles 10 cm under water surface starts when the buoyancy force acting on the bubble is approximately equal to the aerodynamic force in the tube.
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Measurement of acoustic input impedance of the human vocal tract models
Radolf, Vojtěch ; Dlask, P. ; Otčenášek, Z.
Input acoustic impedance of the human vocal tract models made of plexiglass was measured using the measurement system BIAS 6. Three models A, I, U for vowels /a:/, /i:/ and /u:/ had simplified rectangular shape of the channel with constant height 20 mm. The fourth model A2D had elliptical channel shape. Resulted resonance frequencies were within the known ranges of formant frequencies of the vowels. The resonances of default configurations varied for different boundary positions in relation to measuring microphone in the range of 0.5 %, 3.9 %, 2.1%, 6.7 % for the models A2D, A, I and U, respectively. The resonances of direct and reversed models with the output closed differed in the range of 0.5 % and 1.8 % for A2D and A model, respectively. The measured and computed resonances differed in the range from 3.8 % for A2D to 14.6 % for the model I.
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In vivo measurements of air pressure, vocal folds vibration and acoustic characteristics of phonation into a straw and a resonance tube used in vocal exercising.
Radolf, Vojtěch ; Laukkanen, A. M. ; Horáček, Jaromír ; Veselý, Jan ; Liu, D.
The study investigates the differences between three most widely used methods in voice training and therapy: Phonation into a glass resonance tube (1) the outer end in the air, (2) the outer end submerged 2-10 cm below water surface in a bowl (‘water resistance therapy’ with bubbling effect), and (3) phonation into a very thin straw. One female speech trainer served as subject. Acoustic samples, electroglottographic signals and both mean and dynamic airpressures 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. Both phonation threshold and ordinary, most comfortable phonation were recorded.
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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.
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Implementation of 1D mathematical model of vocal cavities into TTS synthesizer – preliminary study
Radolf, Vojtěch ; Horák, Petr
Simplified 1D mathematical models of the human vocal tract were modified for using them in Text-To-Speech systems so that they help to simulate emotional speech. The geometry (area function) of the models for all Czech vowels was modified using the inverse task optimization procedure so that the computed formant frequencies match the measured formant frequencies of utterances of professional speaker. Output acoustic pressure signal generated from the models in wav format sounded satisfactorily for all the vowels and fundamental frequencies varied in an octave range from 77 Hz to 156 Hz. Neverthelles more testing procedures are needed to verify reliability and quickness of the model as well as intelligibility of generated utterances especially in formant TTS system and linear predictive TTS system.
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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.
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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.
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