Tuesday 15 September 2020
Researchers said that more quiet, indoor high-risk areas, such as hospitals and restaurants, could help reduce the risk of coronavirus infection.
The research team explained, in an advance copy of a detailed paper on the study, that in efforts to limit transmission, reducing average levels of speech and speaking by 6 dB could have the effect of doubling the room’s own ventilation, according to the “Russia Today” website.
“The results indicate that public health authorities should consider implementing” quiet zone “measures in high-risk indoor environments, such as hospital waiting rooms or dining facilities,” the six researchers from the University of California, Davis wrote.
And in July, the World Health Organization changed its directives to recognize the potential for aerosol transmission when in restaurants or in fitness classes.
The research paper showed that the microscopic droplets, which come out during speaking, evaporate to leave aerosol particles large enough to carry viable viruses.
A 35 dB increase in loudness, or the difference between a whisper and a shout, increases the particle emission rate by 50 times.
Normal conversation is above the 10 dB range, while ambient noise in restaurants is around 70.
Lead researcher William Restenbart said: “Not all indoor environments are equal in terms of the risk of aerosol transmission. A quiet, crowded classroom is much less risky than an uncrowded bar, where customers are socially distant but chatting and singing to loud music.”