The report, from researchers at the National Institute of Diabetes and Digestive and Kidney Diseases and the University of Pennsylvania, was published in the Proceedings of the National Academy of Sciences, a peer-reviewed journal. It is based on an experiment that used laser light to study the number of small respiratory droplets emitted through human speech.
The answer: a lot.
“Highly sensitive laser light scattering observations have revealed that loud speech can emit thousands of oral fluid droplets per second,” the report states.
Previous research has shown large outbreaks of coronavirus infections in a call center in South Korea where workers were in proximity and in a crowded restaurant in China, and such events have led some experts to suspect that the highly contagious virus can spread through small aerosol droplets. That remains the subject of research and debate, and for now, the consensus among infectious disease experts is the virus is typically spread through large respiratory droplets.
This new study did not involve the coronavirus or any other virus, but instead looked at how people generate respiratory droplets when they speak. The experiment did not look at large droplets but instead focused on small droplets that can linger in the air much longer. These droplets still could potentially contain enough virus particles to represent an infectious dose, the authors said.
Louder speech produces more droplets, they note. The paper estimates that one minute of “loud speaking” generates “at least 1,000 virion-containing droplet nuclei that remain airborne” for more than eight minutes.