Respiratory Particle Production During Phonation: Experimental Measurements in Self-Oscillating Vocal Fold Models

The recent increase in airborne infectious disease outbreaks has underscored the importance of understanding how respiratory particles are generated. To-date, no studies have definitively identified the mechanics of respiratory particle formation produced by vocal fold (VF) oscillations during phonation. This study investigates the fluid-driven mechanisms responsible for particle formation during phonation through the use of synthetic VFs and a bio-physical mimetic respiratory tract lining fluid (RTLF). The synthetic VFs are self-oscillating and replicate the vibratory patterns of phonation, while the bio-physical RTLF mimics the viscoelastic characteristics of human RTLF. The experimental setup enables high-speed visualization of particle formation at the VFs, providing a rare view of source-level generation as a function of the VF kinematics. High-speed video of the glottal opening captures the mechanics responsible for particle formation, including airflow-induced spume droplet formation and capillary bridge breakup during VF motion. The influence of both the rheological properties of the RTLF and phonatory conditions on the mechanics of particle generation are also discussed.