A fresh look at spreading respiratory infections via speech
A fresh look at spreading respiratory infections via speech lead image
COVID-19 and other respiratory infections are well known to be spread by coughing, sneezing, and even just breathing. But they can also be spread by talking. Speech vibrates the vocal folds in the throat and can produce aerosol droplets much like coughing and sneezing; however, little is understood about how these droplets are generated.
Fritzsche et al. developed an experimental setup to study droplet formation during speech, simulating the movement of the vocal folds and the passage of fluid through them. They examined the resulting aerosols with a high-resolution camera and derived particle size distributions.
“With high-speed videos we have shown for the first time how the aerosols are generated,” said author Lisa Fritzsche. “We could unravel details of the aerosol formation mechanisms at the vocal folds which were not reported so far.”
They determined that the primary method of aerosol generation involves the breakup of bubbles across the fold. This method produces smaller, longer lasting aerosols than the breakup of filaments, which was previously assumed to play the dominant role. Larger amplitudes of the vocal folds, associated with louder voices, and higher frequency vibrations, associated with higher pitched voices, led to smaller particles.
The authors hope their pioneering study can serve as a benchmark for future research into aerosol production from speech.
“We are planning a new, more sophisticated test rig which includes more details of the pharynx/larynx and improves the vocal folds’ excitation to oscillate,” said author Katrin Bauer. “Moreover, we plan to adjust the rheological properties of the artificial mucus to more physiological values.”
Source: “Toward unraveling the mechanisms of aerosol generation during phonation,” by L. Fritzsche, R. Schwarze, F. Junghans, and K. Bauer, Physics of Fluids (2022). The article can be accessed at https://doi.org/10.1063/5.0124944 .
This paper is part of the Flow and the Virus Collection, learn more here .
