Ventricular Fold Phonation: Viscoelastic Properties and HSDI

Abstract

Objective: Determine the functional biomechanical properties of the human false vocal fold mucosa at phonatory frequencies, in comparison with those of the true vocal fold cover; and to quantify the vibration patterns of ventricular fold phonation with HSDI (high speed digital imaging). Method: Viscoelastic shear properties of false fold specimens were quantified as functions of frequency, with measurements of elastic shear modulus (G′) and dynamic viscosity (h′) at up to 250 Hz using a simple-shear rheometer. Ventricular fold phonation of three subjects was analyzed by HSDI (high speed digital imaging) through kymography and laryngotopography. Results: All specimens showed similar frequency dependence of their viscoelastic properties, with G′ gradually increasing with frequency and h′ monotonically decreasing with frequency. G′ and h′ of the false fold mucosa were generally higher than those of the true vocal fold cover, although the differences did not reach statistical significance. Kymographic and laryngotopographic analysis of high speed digital images revealed vibration of the false fold mucosa for subjects undergoing ventricular fold phonation. The vibratory frequencies were lower than typical fundamental frequencies for phonation. Conclusion: These findings showed false folds could function as a secondary sound source. These preliminary data suggested that the false fold mucosa could serve as replacement material for patients with unrepairable vocal fold cover damage.