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. 2020 May 21;382(21):2061-2063.
doi: 10.1056/NEJMc2007800. Epub 2020 Apr 15.

Visualizing Speech-Generated Oral Fluid Droplets with Laser Light Scattering

Philip Anfinrud  1 , Valentyn Stadnytskyi  1 , Christina E Bax  2 , Adriaan Bax  1
Affiliations

Visualizing Speech-Generated Oral Fluid Droplets with Laser Light Scattering

Philip Anfinrud et al. N Engl J Med. .
No abstract available

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Figures

Figure 1
Figure 1. Emission of Droplets While a Person Said “Stay Healthy.”
Droplets generated during speech produced flashes as they passed through the light sheet in this experiment. Panel A shows the flash count during each frame of a video produced at a rate of 60 frames per second, with and without a damp cloth covering the speaker’s mouth. Green indicates spoken words. The number of flashes was highest (arrow) when the “th” sound in the word “healthy” was pronounced. The trace offset below the graph shows that when the speaker’s mouth was covered with a damp cloth, there was no qualitative increase in the flash count during speech over the background level observed before the first trial of speech. The flash count during the silent periods between the spoken phrases remained above the background level, a finding that suggests that some of the speech droplets lingered inside the box for some seconds. Panel B shows frame 361 from the video, which corresponds to the red arrow in Panel A and to the highest number of speech droplets visualized in an individual frame of the video recording. The spots vary in brightness because of the differences in the size of the particles. Some of the spots are streaked, which suggests that the rate of 60 frames per second was insufficient to freeze the motion of the droplets. The feature highlighted by a dashed yellow circle corresponds to the tip of a very thin wire positioned just behind the light sheet; this wire provided a reference for setting the camera focus and gain before recording. (See the video, available at NEJM.org.)
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