Objective:
Vocal folds are well documented to exhibit both chaotic and stable oscillatory behavior depending on their initial conditions, tissue parameters, and subglottal pressure. However, the relationship between tissue stress and oscillation phase remains poorly understood, partly due to the complexity of modeling chaotic waveforms and deriving corresponding stress fields. To address this gap, we employ a simplified two-mass vocal fold model to evaluate average tissue stress and investigate its relationship to oscillatory dynamics.

Methods:
Using previously established two-mass model frameworks and derived stress formulations, we simulated a diseased vocal fold with a right-sided polyp in MATLAB to obtain numerical displacement and fundamental frequency data. These results were used to compute corresponding tissue stresses. Polyp size was systematically varied to examine how changes in geometry influence the transition between stable and chaotic oscillations. The convergence of the largest Lyapunov exponent was used to quantify the degree of chaos and establish a connection between dynamic instability and stress variation.

Results:
Our findings demonstrate that tissue stresses differ substantially between diseased and healthy vocal folds and are strongly modulated by the oscillation phase.

Conclusions:
We conclude that chaotic dynamics have a significant impact on tissue stress, providing insight into potential mechanisms of vocal fold injury and pathology progression.