Videokymographic image processing: Objective parameters and user-friendly interface

Vocal Fold Collision Speed in vivo: The Effect of Loudness

Mechanical impact stress on the vocal fold surface, particularly when excessive, has been postulated to cause the so-called phonotraumatic tissue lesions, such as nodules and polyps. The collision stress between the vocal folds depends on the vocal fold velocity at the time of impact. Hence this vocal fold collision speed is a relevant parameter when considering biomechanical economy of phonation, especially in voice professionals needing a louder voice than normal. Combining a precise photometric measurement of glottal area and simultaneous measurements of translaryngeal impedance (electroglottogram) for identifying the time of the maximum rate of increase of vocal fold contact allows computing the vocal fold collision speed in a wide range of loudnesses. The vocal fold collision speed is - for modal voicing - always smaller than the maximum vocal fold velocity during the closing phase, but it strongly increases with intensity. Moreover, this increase shows a biphasic pattern, with a significant enhancement from a certain value of dB on. Understanding physiological variables that influence vocal fold collision forces provides relevant insight into the pathophysiology and the prevention of voice disorders associated with phonotraumatic vocal hyperfunction.

Intraglottal Aerodynamics at Vocal Fold Vibration Onset

The most frequently observed type of voice onset in spontaneous speech in normal subjects is the soft onset, and it may be considered as the "physiological" onset. It starts from an immobile narrow glottal slit crossed by a continuous airflow, and then a few oscillations (even a single one in some cases) precede the first glottal closure. It is a transient event, during which the acting forces, lung pressure, intraglottal pressure, myoelastic tension of the vocal fold (VF) oscillator and inertance of the supraglottal vocal tract, interact to progressively reach the steady state of a sustained oscillation. Combined measurements of flow, area, and pressure provide a detailed qualitative and quantitative analysis of the intraglottal mechanical events at the precise moment of starting oscillation in a physiological (soft or soft/breathy) onset. Our in vivo measurements of airflow and glottal area show that the very first oscillation occurs exactly at the time when turbulence appears at the level of the glottal narrowing, ie, when the Reynolds number reaches its critical value. The turbulence may be assumed to trigger an oscillator consisting in the ensemble of the VFs and the air of the vocal tract, which is known to be weakly damped. Turbulence can act here as an aspecific flick, triggering the oscillator, the frequency of oscillation being determined by its mechanical properties. Furthermore, the first noticeable glottal oscillations are sinusoidal: the VFs are neither steeply sucked together by a negative Bernoulli pressure, nor burst apart by the lung pressure. Our measurements show that, at the critical time, the rising positive lung pressure is balanced by the rising negative Bernoulli pressure generated by the transglottal flow.

Physiology and Acoustics of Inspiratory Phonation

INTRODUCTION

Inspiratory phonation (IP) means phonating with inspiratory airflow. Some vocalists remarkably master this technique, to such an extent that it offers new dramatic, aesthetic, and functional possibilities in singing specific contemporary music. The present study aims to a better understanding of the physiological backgrounds of IP.

MATERIAL AND METHODS

A total of 51 inhaling utterances were compared with 61 exhaling utterances in a professional soprano highly skilled in inhaling singing, by means of high-speed single-line scanning and advanced acoustic analysis. Ranges of intensity and Fo were kept similar.

RESULTS

The main differences are: (1) an inversion of the mucosal wave, (2) a smaller closed quotient in IP, (3) a larger opening/closing quotient in IP with the additional difference that in IP, the quotient is larger than 1 (opening slower than closing), whereas it is less than 1 in expiratory mode (opening faster than closing), (4) a larger vocal-fold excursion in IP, (5) higher values of adaptive normalized noise energy in IP, and (6) a steeper slope of harmonic peaks in IP. However, jitter values are similar (within normal range), as well as damping ratios and central formant frequencies. The two voicing modes cannot be differentiated by blind listening.

CONCLUSION

The basic physiological mechanisms are comparable in both voicing modes, although with specific differences. IP is actually to be considered as an "extended vocal technique," a term applied to vocalization in art music, which falls outside of traditional classical singing styles, but with remarkable possibilities in skilled vocalists.

Automated tracking of quantitative parameters from single line scanning of vocal folds: a case study of the 'messa di voce' exercise

This article presents a novel application of the 'single line scanning' of the vocal fold vibrations (kymography) in singing pedagogy, particularly in a specific technical voice exercise: the 'messa di voce'. It aims at giving the singer relevant and valid short-term feedback. A user-friendly automatic analysis program makes possible a precise, immediate quantification of the essential physiological parameters characterizing the changes in glottal impedance, concomitant with the progressive increase and decrease of the lung pressure. The data provided by the program show a strong correlation with the hand-made measurements. Additional measurements such as subglottic pressure and flow glottography by inverse filtering can be meaningfully correlated with the data obtained from the kymographic images.

Kymographic imaging of laryngeal vibrations

PURPOSE OF REVIEW

Kymographic imaging is a modern method for displaying and evaluating vibratory behaviour of the vocal folds which is crucial for voice production. This review summarizes the state of the art of this method, and focuses on the progress in this area within the last 5 years.

RECENT FINDINGS

Videokymography, using a special videocamera, offers high-speed (video)kymographic images in real time, which is advantageous in daily clinical practice. Two other methods use software to create kymograms retrospectively: digital kymography processes high-speed videolaryngoscopic recordings and offers numerous research possibilities, whereas strobovideokymography processes videostroboscopic recordings, and its use is limited to regular vibration patterns. Current studies reveal that high-speed kymographic images allow more reliable visual evaluation of vibrations than by watching video recordings. Image analysis procedures have been advanced to quantify the vibration properties of the vocal folds. New information has been obtained on asymmetry, mucosal waves, irregularities, phonation onset, and nonlinear dynamic phenomena in voice disorders, as well as in singing.

SUMMARY

High-speed kymography visualizes vibratory features which are not simply observable via traditional methods. It shows large potential in better understanding the functional origin of hoarseness and unsteady phonatory states. Further research in this area is envisioned.

Vocal fold vibration amplitude, open quotient, speed quotient and their variability along glottal length: kymographic data from normal subjects

Abstract Quantitative knowledge about healthy vocal fold vibration characteristics provides the basis for an objective assessment of vocal fold vibrations. In this study, using high-speed videolaryngoscopy the alterations of the relative vibration amplitudes, open quotients, and speed quotients were analyzed along the glottal length in 30 male and 30 female healthy subjects. The maximum vibration amplitude was identified at 41.1% ± 10.8% and 46.5% ± 18.0% of the visible glottal length in females and males, respectively. The average open quotients decreased in females and males from posterior to anterior, while the speed quotients did not change systematically. The reported normative values can be used to distinguish normal and abnormal vibrations in clinical practice when aiming at quantitative diagnosis of functional voice disorders.