A paper everyone should look at

Proc. Natl. Acad. Sci. vol. 117 pp. 25237–25245 ’20 presumably is ‘freely shared’. Here’s the link — https://www.pnas.org/content/pnas/117/41/25237.full.pdf

The authors set up a mist of fine water droplets in front of a speaker and watch what the emitted air does to them (using high speed cameras). Sentences with a lot of plosives (such as p) e.g. peter piper picked a peck of pickled peppers produce a jet which barrels along for a few meters. Different sound produce air flows in different directions. The pictures are incredible. If viruses are carried along with this, the implications for the pandemic flu are obvious. Wear a mask when talking to strangers.

Here’s a quote from the paper “We show that the transport distance of exhaled material versus time, in the form of three distinct scal- ing laws, represents the typical structure of the flow, including 1) a short (<0.5 m) distance, with large angular variations, where the complexity of language is evident and responsible for mate- rial transport in a fraction of a second; 2) a longer distance, out to approximately 1 m, where directed transport occurs driven by individual vortical puffs corresponding roughly to individual plo- sive sounds; and 3) a distance out to about 2 m, or even farther, where spoken sentences with plosives, corresponding effectively to a train of puffs, create conical, jet-like flows. “

Well, those are just words — if you do nothing else, look at the pictures in the paper.

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  • Rhenium  On October 21, 2020 at 12:47 pm

    That does make sense that one of the earliest super-spreading occurrences was at (I believe) a choir practice. Also a good reason to limit religious attendance numbers (density) due to the higher average age and propensity for singing.

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