Atelier Voix Chantée n°11

The role of the vocal folds and the vocal tract on registers and their transitions

Intervenant :  Matthias Echternach, ORL at the Institute of Musicians' Medecine (Freibourg University, Germany) and singer
Date : 22/01/09

Présents : Christophe d'Alessandro, Elena Berardi, Marie-Cécile Barras, Michèle Castellengo, Boris Doval, Matthias Echternach, Robert Expert, Nathalie Henrich, Mélanie Guérin, Sylvain Lamesch, Yves Ormezzano, Sophie Quattrocchi, Anne Rialland, Bernhard Richter, Bernard Roubeau, Coralie Vincent.nbsp;

Résumé : 
Since the first descriptions of voice registers, physiological voice research has focused on both the voice source and how it is being influenced by the vocal tract. Electroglottography (EGG) as well as inverse filtering have shown that clear modifications occur during register transitions in both male and female voices. The transition is sometimes accompanied by fundamental frequency (F0) discontinuities which have been explained by nonlinear dynamics phenomena . The contact quotient (CQ) as measured by EGG as well as the closed quotient as measured by inverse filtering thus seem lower in falsetto than in modal register. Register transitions have also been observed to be accompanied by irregular vocal fold vibrations; clear-cut modifications of the vocal fold vibrations have been documented by both stroboscopic and videokymographic examinations. Irregular vocal fold vibrations during register transition will cause an F0 irregularity, i.e., jitter. In the first part of the presentation studies on untrained and trained (i.e. professional tenors and counter tenors) subjects are demonstrated revealing an increase of both, perturbation values by means of analysis of the EGG and Audio-signal and irregularities in analysis of high speed imaging. Both kinds of investigations suggest that register transitions are accompanied with instabilities of vocal fold oscillations. In the second part of the presentation research on the modifications of the vocal tract due to register shifts in professional singers is presented. In this study dynamic real time MRI up to 10 frames per second was used to analyze the vocal tract profile in 10 professional opera tenors, who sang an ascending scale from C4 to A4 on the vowel /a/, and 6 counter tenors, who sang an ascending scale from G3 to E4. The investigations in the tenors included their register transition to falsetto and in a second condition a continuation of the modal register throughout the passaggio which the author refer as voix mixte. Modal to falsetto register changes were associated with minor vocal tract modifications, including elevation of the larynx and a lifted tongue dorsum. Transitions to voix mixte, by contrast, were associated with great vocal tract modifications. Under these conditions, the subjects widened their pharynges, their lip and jaw openings, and increased their jaw protrusion. These modifications were stronger in more “heavy” tenors than in more “light” tenors. Last, preliminary data on the counter tenors suggest an strong influence of the position of the tongue with respect to their counter tenor voice.