Objective: The aim of this study was to describe and analyze the vibratory pattern of vocal folds in an asymmetric situation. Study design and setting: 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. Results: All experiments showed periodic vibration. A phase shift was noted between the two vocal folds. Subharmonics and biphonation were identified in all the experiments. Conclusion: Lax vocal folds were more susceptible to spectral changes with increasing airflow. Significance: 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. © 2006 American Academy of Otolaryngology-Head and Neck Surgery Foundation. Inc.1353438444Woodson, G., Configuration of the glottis in laryngeal paralysis: clinical study (1993) Laryngoscope, 103, pp. 1227-1234Woodson, G.E., Murry, M.P., Schweizer, V., Unilateral cricothyroid contraction and glottic configuration (1998) J Voice, 12, pp. 335-339Faaborg-Andersen, K., Electromyographic investigation of intrinsic laryngeal muscles in humans (1957) Acta Physiol Scand, 41, pp. 140-167Dedo, H.H., Hall, W.N., Electrodes in laryngeal electromyography. Reliability comparison (1969) Ann Otol Rhinol Laryngol, 78, pp. 172-180Nasseri, S.S., Maragos, N.E., Combination thyroplasty and the "twisted larynx:" combined type IV and type I thyroplasty for superior laryngeal nerve weakness (2000) J Voice, 14, pp. 104-111Koufman, J.A., Belfsky, P.C., Unilateral or localized Reinke's edema (pseudocyst) as a manifestation of vocal fold paresis: the paresis podule (2001) Laryngoscope, 111, pp. 576-580Eckley, C.A., Sataloff, R.T., Hawkshaw, M., Voice range in superior laryngeal nerve paresis and paralysis (1998) J Voice, 12, pp. 340-348Ableson, T.I., Tucker, H.M., Laryngeal findings in superior laryngeal nerve paralysis: a controversy (1981) Otolaryngol Head Neck Surg, 89, pp. 463-470Tanaka, S., Hirano, M., Umeno, H., Laryngeal behavior in unilateral superior laryngeal nerve paralysis (1994) Ann Otol Rhinol Laryngol, 103, pp. 93-97Hirano, M., Ohala, J., Vennard, W., The function of laryngeal muscles in regulating fundamental frequency and intensity of phonation (1969) J Speech Hear Res, 12, pp. 616-628Atkinson, J.E., Correlation analysis of the physiological factors controlling fundamental voice frequency (1978) J Acoust Soc Am, 63, pp. 211-222Dursun, G., Sataloff, R.T., Spiegel, J.R., Superior laryngeal nerve paresis and paralysis (1996) J Voice, 10, pp. 206-211Arnold, G.E., Physiology and pathology of the cricothyroid muscle (1961) Laryngoscope, 71, pp. 687-753Mygind, H., Die paralyse des musculus cricothyroideus (1906) Arch Otolaryngol, 18, pp. 403-418Giovanni, A., Ouaknine, M., Guelfucci, B., Non linear behavior of vocal fold vibration in an experimental model: role of coupling between the vocal folds (1999) J Voice, 3, pp. 465-476Ouaknine, M., Garrel, R., Giovanni, A., Separate detection of vocal fold vibration by optoreflectometry: a study of biphonation on excised porcine larynges (2003) Folia Phoniatr Logop, 55, pp. 28-38Titze, I., Baken, R., Herzel, H., Evidence of chaos in vocal fold vibration (1993) Frontiers in basic science, pp. 143-188. , Titze I. (Ed), Singular Publishing Group, San DiegoRemacle, M., Trigoux, I., Characteristics of nodules through the high-resolution frequency analyzer (1991) Folia Phoniatr, 43, pp. 53-59Berry, D.A., Herzel, H., Titze, I.R., Bifurcations in excised larynx experiments (1996) J Voice, 10, pp. 129-138Isshiki, N., Tanabe, M., Ishizaka, K., Clinical significance of asymmetrical vocal cord tension (1977) Ann Otol, 86, pp. 58-66