Induced asymmetries in an excised larynx model: Impact of mucus characteristics on dynamics and acoustics

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Voice disorders do not only result from anatomical tissue alterations in the vocal folds. The phonation process is a complex interaction between airflow, laryngeal tissue structures, mucosal surface layer (i.e. mucus) and the resulting acoustic outcome. The functionality of this fluid-structure-acoustic interaction can be disturbed by left-right asymmetries in the dynamical behavior and insufficient closure of the vocal folds during oscillation; i.e. the phonation process is disturbed and the voice quality is reduced. This project is based on the hypothesis that the coupling between the contributory factors of phonation is highly dependent and influenced by the mucus layer that covers the vocal folds and represents the natural boundary layer between airflow and tissue. Up to date, this interrelation has been neglected in phonation studies. The identification and quantification of a compensatory mechanism of mucus on dynamics and hence the acoustics would be highly desirable in guiding voice quality for non-invasive treatment.The central objective of this project is the investigation of laryngeal mucus and its role in the cause-and-effect chain of the phonation process. Hence, synthetic mucus will be created with characteristic viscoelastic properties in the range of natural human mucus samples. The influence of the synthetic mucus samples towards the phonation process will be tested in the computer controlled experimental setup which was developed in the previous project phase. This setup enables variable adjustment of the laryngeal boundary conditions (i.e. induced asymmetry and glottal gap) and simultaneous multimodal measurements (i.e. high-speed videoendoscopy, flow, subglottal pressure, acoustic signal). This will allow a thorough quantification of all the contributing factors and reveal the causal interrelations in phonation. The ex vivo studies will be performed using excised porcine larynges received from the local slaughterhouse.