|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
Computer simulation of musical singer’s voice based on MRI and acoustic measurement
Radolf, Vojtěch ; Nissinen, A. ; Laukkanen, A. M. ; Havlík, R. ; Horáček, Jaromír
An inverse method was used to estimate the vocal tract geometry as a 1D model on the basis of acoustical characteristics of a professional musical singer before and after vocal exercising. The basic geometrical data for the model were obtained from MRI registered during sustained phonation of vowels [a:], [i:], [u:] produced in naive and professional ways. The model was used for numerical simulations of the voice signals. The results of simulation were compared to the acoustic recordings. According to the results, a singer’s formant cluster was accomplished after exercising. It seemed to be due to lowering of the larynx and lengthening and narrowing of the epilarynx. There was a qualitative agreement between 3D measurements of MRI and the results of modeling. The results suggest that for a singer’s formant cluster a relatively low pharynx over epilarynx ratio may be sufficient, at least if the larynx lowers.
|
guest ::
