Previous studies have shown the importance of cricothyroid muscle activation in altering fundamental frequency in the human voice. Other studies have investigated the non-linear properties of vocal fold tissue and the impact of this non-linearity on frequency response. Several physical models of the vocal folds have been made for research purposes. However, all have been isotropic in nature with linear stress-strain properties. The purpose of this study was to create a physical model with

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... near stress-strain properties to investigate the frequency response of the model as cricothyroid muscle activation was simulated (in other words, as the vocal folds were stretched in an anterior-posterior dimension). In this study the physical models of the vocal folds were stretched in 1 mm increments and the fundamental frequency (F 0 ) was recorded at each position. Subglottal pressure was also monitored and phonation threshold pressures were recorded for each adjustment in length and vocal fold tension, because this can influence F 0 . Results were obtained for models with and without non-linear properties for comparison. Tensile tests were also conducted for the linear and non-linear synthetic vocal folds. Results indicate that non-linear models demonstrated a more substantial frequency response than linear vocal fold models and a more predictable F 0 increase with respect to increasing vocal fold length. Phonation threshold pressures also increased with increasing vocal fold length for non-linear vocal fold models. This trend was reversed for linear vocal fold models, with phonation threshold pressures decreasing with increasing vocal fold length. These results indicate that the non-linear vocal fold models more accurately represent the human vocal folds than do linear models. This study serves as the foundation for future research to quantify the impact of non-linear tissue properties versus active tensioning (through antagonistic thyroarytenoid muscle activation) on F 0 response and phonation threshold pressure.