Time Spent Talking, Not Just Physical Distance, Plays Role In Covid-19 Spread Researchers Say
Stay six feet apart — that’s the rule of thumb when it comes to social distancing. However, a new study suggests we need to take speech into account in addition to physical distancing when creating Covid-19 transmission mitigation strategies. By assessing the physics of saliva droplet formation and subsequent spray while a person speaks, researchers have shown the words we say play a role in how many droplets we spread — and how far they go.
The paper, published in Physical Review Fluids, explores the mechanics behind transmission of droplets through speech. Manouk Abkarian of the University of Montpellier, France, and Howard Stone of Princeton University used high-speed videos to study how a talking person forms saliva droplets.
“Since there are many excellent studies on the size of droplets formed in some of these activities, we decided to study the airflows that would carry small droplets and aerosols from one person to another in casual interaction such as speaking,” says Stone, a professor of Mechanical and Aerospace Engineering with research interests in fluid dynamics.
Previous studies have also explored the role of speech in Covid-19 transmission. Earlier this year, researchers from the National Institutes of Health used laser light to observe droplet production. Their findings revealed that a person talking loudly even for just a second will emit thousands of droplets. Ironically, they found the phrase “stay healthy” is especially effective in sending saliva spraying, due to the pronunciation of “th.”
Similarly to the NIH study, Abkarian and Stone’s research suggested the length a person speaks is a more important factor in droplet spread than has been discussed in social distancing conversations thus far. “We were basically discovering that a ‘distance of security’ made no sense without introducing time in the problem,” says