Speak softly and scatter fewer coronavirus particles, say
researchers

TOKYO – More quiet zones in high-risk indoor spaces, such
as hospitals and restaurants, could help to cut coronavirus contagion risks,
researchers have said, after a study showed that lowering speaking volume can
reduce the spread of the disease.

In efforts to rein in transmission, a reduction of 6
decibels in average speech levels can have the same effect as doubling a room’s
ventilation, scientists said on Wednesday, in an advance copy of a paper
detailing their study.

“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,” wrote the six
researchers from the University of California, Davis.

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

Microscopic droplets ejected while speaking evaporate to
leave behind aerosol particles big enough to carry viable virus, the paper
showed. An increase of about 35 decibels in loudness, or the difference between
whispering and shouting, boosts the particle emission rate by 50 times.

Not all environments equal

Normal conversation is above the 10-decibel range, while
ambient noise in restaurants is around 70.

“Not all indoor environments are equal in terms of
aerosol transmission risk,” said lead researcher William Ristenpart.

“A crowded but quiet classroom is much less
dangerous than an uncrowded karaoke bar where patrons are socially distanced
but talking and singing over loud music.”

The global death toll from the virus passed 900 000 on
Wednesday, as worldwide cases topped 27.7 million, according to a Reuters
tally.

An average of more than 5 600 people die each day,
according to Reuters calculations.

 – REUTERS