Lowering speaking volume can reduce transmissibility of coronavirus, researchers say, a finding that could have implications for the management of high-risk indoor spaces such as hospitals and restaurants.

A 6-decibel reduction in average vocalisation intensity can have the same effect in curbing contagion risks as doubling the ventilation rate in a room, researchers from the University of California Davis say in a study posted on the arXiv preprint server.

“The results suggest that public health authorities should consider implementing ‘quiet zones’ in high-risk indoor environments, such as hospital waiting rooms or dining facilities,” the researchers wrote.

The WHO changed its guidance in July to acknowledge the possibility of aerosol transmission, such as during choir practice, in restaurants or in fitness classes.