Reducing the number of vocal fold mechanical tissue properties: evaluation of the incompressibility and planar displacement assumptions.

The incompressibility and planar displacement assumptions were used to reduce the number of independent tissue parameters required for the characterization of a structural model of the vocal folds. The influence of these simplifying assumptions on the vibratory properties of the model was investigated. The purpose was to provide estimates of the error introduced by these assumptions. The variability in human tissue properties was accounted for through systematic variation of several material parameters. The modal properties of a vocal fold structural model were computed with each assumption and, in turn, were relaxed to determine their respective effects. The results indicated that the incompressibility assumption introduces little error. Errors introduced by the planar displacement assumption were found to depend on the ratio of the longitudinal stiffness and the transverse stiffness. Criteria for determining the compatibility of tissue property values from independent studies are also presented.