Biaxial mechanical properties of human vocal fold cover under vocal fold elongation.

Mechanical properties of the human vocal fold cover layer were experimentally investigated in uniaxial and biaxial tensile tests. The results showed a coupling effect between the stress conditions along the anterior-posterior and transverse directions, with vocal fold elongation increasing vocal fold stiffness along both directions, thus allowing more efficient control of the fundamental frequency of voice through vocal fold elongation. This study also shows that vocal folds were nearly isotropic at resting conditions, thus a tendency to vibrate with incomplete glottal closure, but became increasingly anisotropic with increasing vocal fold elongation.