Three-dimensional biomechanical properties of human vocal folds: Parameter optimization of a numerical model to match in vitro dynamics

Abstract

The human voice signal originates from the vibrations of the two vocal folds within the larynx. The interactions of several intrinsic laryngeal muscles adduct and shape the vocal folds to facilitate vibration in response to airflow. Three-dimensional vocal fold dynamics are extracted from in vitro hemilarynx experiments and fitted by a numerical three-dimensional-multi-mass-model (3DM) using an optimization procedure. In this work, the 3DM dynamics are optimized over 24 experimental data sets to estimate biomechanical vocal fold properties during phonation. Accuracy of the optimization is verified by low normalized error (0.13 6 0.02), high correlation (83% 6 2%), and reproducible subglottal pressure values. The optimized, 3DM parameters yielded biomechanical variations in tissue properties along the vocal fold surface, including variations in both the local mass and stiffness of vocal folds. That is, both mass and stiffness increased along the superior-to-inferior direction. These variations were statistically analyzed under different experimental conditions (e.g., an increase in tension as a function of vocal fold elongation and an increase in stiffness and a decrease in mass as a function of glottal airflow). The study showed that physiologically relevant vocal fold tissue properties, which cannot be directly measured during in vivo human phonation, can be captured using this 3D-modeling technique.

Dynamic vocal fold parameters with changing adduction in ex-vivo hemilarynx experiments

“…However, except for numerical models, [34][35][36] a supplementary investigation of the medial surface dynamics is nearly impossible. Therefore, in this work, we performed ex-vivo experiments with three human cadaver hemilarynges.…”

A Deep Neural Network Based Glottal Flow Model for Predicting Fluid-Structure Interactions during Voice Production

“…The model has been extensively used for studying the physics of voice production in both normal and pathological conditions [4][5][6][7][8][9][10]. A shortcoming of this type of model is the lack of physiological correlation between tissue properties and model system parameters [11,12]. Although some effort has been made to establish these relationships [13,14], direct clinical applications are still difficult because a realistic representation of laryngeal physiology is often required in clinics.…”

A finite element study on the cause of vocal fold vertical stiffness variation

“…In this way, the modulus increased linearly (Goodyer et al, 2010) from the superior aspect to the inferior aspect according to the specified VMD. Yang et al (2012) showed that all the stiffnesses (lateral, vertical, and longitudinal) have vertical variation. Thus in the current study, in each case all the three moduli (transverse Young's modulus, longitudinal Young's modulus, and longitudinal shear modulus) were varied simultaneously with the same VMD.…”

“…This vertical stiffness variation was proposed to be important for phonation as it can promote the divergent angle during the vibration (Oren et al, 2014). Beside experimental measurements, vertical stiffness variation has also been common in spring-mass vocal fold models (see, e.g., Ishizaka and Flanagan, 1972;Story and Titze, 1995;Yang et al, 2010;Yang et al, 2012). Yang et al (2012) showed that it is essential to have this feature in order for the spring-mass models to match in vivo vocal fold kinematics.…”

“…Beside experimental measurements, vertical stiffness variation has also been common in spring-mass vocal fold models (see, e.g., Ishizaka and Flanagan, 1972;Story and Titze, 1995;Yang et al, 2010;Yang et al, 2012). Yang et al (2012) showed that it is essential to have this feature in order for the spring-mass models to match in vivo vocal fold kinematics. They suggested that these results support the proposition by Goodyer et al (2010) that the vertical stiffness variation may provide a more efficient transfer of energy across the air/tissue boundary.…”