Voiced sounds production is a result of complex interactions between fluid flow and mechanical behavior of laryngeal tissues. Therefore, during the last decades, numerous experimental, theoretical and computational works have been performed to characterize both aerodynamics of glottal airflow and vocal folds vibrations during human phonation. Yet, the majority of these works have focused on the specificities of glottal self-sustained oscillations once installed, and main physical models of laryngeal source are initialized in a prephonatory position close to glottal adduction. The transient dynamics from respiratory phase to phonatory phase is still poorly understood. This is partly due to the lack of investigations of glottal motion during human breathing. Therefore, the objective of the present study is to characterize the glottis dynamics in the context of respiratory biomechanics and to quantify its impact on fluid/structure interactions within the larynx. This work will rely on an original numerical flow modeling in upper airways, accounting for the glottal geometry observed during a respiratory cycle and corresponding to realistic inspiratory and expiratory flow rates. The proposed methodology combines an in-vivo exploratory approach based on medical imaging with a numerical approach. At first, an idealized volume geometry of the upper airways is reconstructed using anatomical data extracted from CT-SCAN images acquired in glottal static conditions. Then, the physiological correlates of a complete respiratory cycle are observed by means of video recording of laryngofibroscopic examination and synchronized oral airflow measurements. Glottal dynamics can then be deduced from an image processing analysis and used for the elaboration of a parametrical mechanical model of the glottal aperture. Finally, numerical flow simulations are realized in the complete geometry, using measured oral airflows and glottal geometries during inspiration and expiration. Simulated aerodynamics of the glottal jet are studied and compared in stationary and physiological instationary flow conditions, for both motionless and realistic glottal configuration.
Glottal dynamics and laryngeal airflow during human breathing