To the Editor:
Aerosols and droplets generated during speech have been implicated in the person-to-person transmission of viruses,1,2 and there is current interest in understanding the mechanisms responsible for the spread of Covid-19 by these means. The act of speaking generates oral fluid droplets that vary widely in size,1 and these droplets can harbor infectious virus particles. Whereas large droplets fall quickly to the ground, small droplets can dehydrate and linger as “droplet nuclei” in the air, where they behave like an aerosol and thereby expand the spatial extent of emitted infectious particles.2 We report the results of a laser light-scattering experiment in which speech-generated droplets and their trajectories were visualized.
The output from a 532-nm green laser operating at 2.5-W optical power was transformed into a light sheet that was approximately 1 mm thick and 150 mm tall.