In vivo observations of salivary filament breakup inside human vocal cords

We describe high-speed and stroboscopic videos using a laryngoscope (i.e., a camera inserted through the mouth or through the nose) to directly visualize human vocal folds during phonation. Our preliminary observations suggest that salivary filaments or ‘strings’ form and break during each oscillation of the vocal folds, with the approximate location of each new filament conserved between cycles. We designed custom image analysis software to quantify the dynamics of filament formation and breakup across several individuals. Based on these preliminary observations, we provide statistics of individual variation in filament formation and its dependence on vocalization loudness and frequency. We anticipate the insights gained from this research will reveal mechanisms of salivary droplet generation during phonation and enhance our understanding of airborne disease transmission.