Effects of vocal fold oscillation characteristics on the aerosol droplet production

Abstract

Although a large number of aerosol droplets are known to be produced from the human larynx during vocalizations, it remains unclear how vocal fold oscillations are involved in the droplet production. In this study, we synthesized vocalizations using two types of silicone vocal fold models and investigated the effects of these model configurations on the droplet production mechanisms by measuring the particle concentrations when artificial mucus was injected into the artificial larynx. One model, which oscillates with complete glottal closure, produced louder sounds with droplets, whose diameter ranged primarily from 0.3 to 2μm. In contrast, the other model, which oscillates without vocal fold collision, produced smaller sounds with droplets having larger diameters. Additional observations using the laser sheets and high-speed imaging demonstrated that the liquid films were formed just above the vocal folds when a constant jet flow was generated in the model which does not exhibit complete glottal closure. These results describe how different oscillation characteristics of the vocal folds may cause differences in droplet concentration.