Vibratory pattern of vocal folds under tension asymmetry.

Abstract

The aim of this study was to describe and analyze the vibratory pattern of vocal folds in an asymmetric situation. Cricothyroid muscle unilateral action was simulated on excised larynges on an experimental bench. Increasing airflow rates were applied to achieve vocal fold vibration. Electroglottography and an optoreflectometer device allowed analysis of separate and simultaneous vocal fold vibration. Spectra of the signals were obtained for each level of airflow variation. All experiments showed periodic vibration. A phase shift was noted between the two vocal folds. Subharmonics and biphonation were identified in all the experiments. Lax vocal folds were more susceptible to spectral changes with increasing airflow. Knowledge of the consequences of mass, tension, and position asymmetries of the vocal folds is crucial for diagnosis making and defining therapeutic strategies in dysphonic patients. This study may contribute to the understanding of physiology of vocal fold interaction and its compensatory mechanisms.