Aerodynamic and acoustic effects of false vocal folds and epiglottis in excised larynx models

Objectives: The purpose of this study was to examine the aerodynamic and acoustic effects of the false vocal folds and the epiglottis on excised larynx phonation. Methods: Several canine larynges were prepared and mounted over a tapered tube that supplied pressurized, heated, and humidified air. Glottal adduction was accomplished either by using two-pronged probes to press the arytenoids together or by passing a suture to simulate lateral cricoarytenoid muscle activation. First, the excised larynx with false vocal folds and epiglottis intact was subjected to a series of pressure-flow experiments with longitudinal tension and adduction as major control parameters. Then, the epiglottis and finally the false vocal folds were removed and the experiment was repeated. The subglottal pressure and the electroglottographic, flow rate, audio, and sound pressure signals were recorded during each experiment. Glottal flow resistance was calculated from the pressure and flow signals. The electroglottographic signal was used to extract the fundamental frequency. Results: It was found that the false vocal folds and the epiglottis offer a positive contribution to the glottal resistance and sound intensity of the larynx. Also, vocal fold elongation and glottal medial compression caused an increase in glottal resistance. The pressure-flow relationships were approximately linear regardless of the structure. Conclusions: The addition of the supraglottic laryngeal structures has a significant impact on both aerodynamic and acoustic characteristics of excised larynges.