Vojtech Radolf

The Czech Academy of Sciences | AVCR · Institute of Thermomechanics

Objective Mechanical buzzers have been developed to clear excessive mucus from the lungs and trachea. Recently, they have been tested for voice therapy. By rapidly interrupting airflow they cause an oscillation of oral pressure, resembling phonation through a tube into water, which is traditionally used in voice therapy (water resistance therapy, W...

Objective The aim of this study was to investigate how the maximum area declination rate (MADR) of the glottis corresponds to the maximum velocity of the self-oscillating vocal folds just before their collision. The maximum velocity before collision is closely related to impact stress in the colliding vocal folds and, thus, it is an important indic...

Flutter instabilities of structures are mostly unwanted phenomena in technical applications excluding some energy harvesting systems that utilize wind or water flow-induced aeroelastic instabilities of the systems. Another situation is in biomechanics of voice where the flutter instability of human vocal folds is a necessary condition for singing a...

Nasal cavities are known to introduce antiresonances (dips) in the sound spectrum reducing the acoustic power of the voice. In this study, a three-dimensional (3D) finite element (FE) model of the vocal tract (VT) of one female subject was created for vowels [a:] and [i:] without and with a detailed model of nasal cavities based on CT (Computer Tom...

Purpose Phonations into a tube with the distal end either in the air or submerged in water are used for voice therapy. This study explores the effective mechanisms of these therapy methods. Method The study applied a physical model complemented by calculations from a computational model, and the results were compared to those that have been report...

Objectives: Water resistance voice therapy applies phonation into water through a tube. This study investigates how strenuous this therapy can be for the vocal folds in terms of impact stress (IS). It further examines whether it is possible to estimate the IS using the contact quotient (CQ) and maximum derivative from an electroglottogram (EGG)....

Objectives: Phonation through a tube in water is used in voice therapy. This study investigates whether this exercise may increase mechanical loading on the vocal folds. Study design: This is an experimental modeling study. Methods: A model with three-layer silicone vocal fold replica and a plexiglass, MK Plexi, Prague vocal tract set for the...

Phonation into a tube that lowers the acoustic vocal tract resonance frequency and increases vocal tract impedance is used in voice therapy to establish effortless voice production. Additionally, keeping the distal end of the tube in the water results in the water bubbling and a consequent oscillation of oral pressure. This may feel like a massage...

Objective: This study compares the flow resistance of Resonance tube (RT) and Lax Vox tube (LVT) when submerged 2 cm and 10 cm in water, as well as phonation into the tubes in these conditions. Methods: In the in vitro experiment, the air pressure for flow rates of 60-600 mL/s was measured at the tube inlet, when the outer end of the tube was su...

The study compares results of in vitro measurements of phonation characteristics performed on three types of originally developed 1:1 scaled artificial models of human vocal folds. The measured aerodynamic, vibration and acoustic characteristics are in good agreement with the values found in humans.

The present contribution discusses a measurement of impact stress in a replica of the vocal folds made of silicon rubber excited by airflow with synchronous registration of the flow-induced vocal fold vibrations using a high speed camera, measurement of the subglottal dynamic and mean air pressures and the radiated acoustic pressure. Special miniat...

Piriform sinuses (PS), side branches of the human vocal tract, produce extra resonances and antiresonances which influence the quality of produced voice. These acoustic resonant characteristics can be numerically simulated by 3D finite element models of the vocal tract with lateral cavities. Computations that use these accurate methods are very tim...

The contribution describes PIV (Particle Image Velocimetry) measurement of airflow in the glottal region of com-plex physical models of the voice production that consist of 1 : 1 scaled models of the trachea, the self-oscillating vocal folds and the human vocal tract with acoustical spaces that correspond to the vowels /a:/, /u:/ and /i:/. The time...

A strong peak between 3 and 4 kHz in the long-term average spectrum (LTAS) of speech has been found to be one correlate of a good male speaking voice, for example, among actors. The actor's or speaker's formant (resembling the singer's formant) can be established by certain vocal training. This study investigates the origin of the speaker's formant...

The measurement of the airflow in a specially developed 1 : 1 scaled complex physical model of the voice production is described. This model consists of simplified models ofthe trachea, the self-oscillating vocal folds and the vocal tract with acoustical spaces that correspond to the vowel [a:]. The measurement set-up enabled to use the Particle Im...

An inverse method was used to estimate the vocal tract geometry as a 1 D 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 magnetic resonance images (MRI) registered during sustained phonation of vowels [a:], [i:], [u:] pro...

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...