Researchers from Princeton University found that normal conversations can create a conical ‘jet-like’ airflow that carries droplets for metres. Howard Stone, one of the researchers on the study, said: “People should recognise that they have an effect around them. It's not just around your head, it is at the scale of metres.”
In the study, the researchers used a high-speed camera to film the movement of droplets from a person saying several different phrases next to a sheet. The phrases ranged from short statements like "we will beat the coronavirus " to nursery rhymes including "Peter Piper picked a peck" and "Sing a song of six pence."
The videos revealed that plosive sounds like ‘P’ create puffs of air in front of the speaker, resulting in a cone-shaped ‘jet-like’ airflow from the speaker’s mouth. Worryingly, this airflow could easily and quickly carry tiny particles away from the speaker, according to the team.
Meanwhile, even short phrases were found to move particles beyond the one-metre distancing recommended by the World Health Organisation. Dr Stone said: “If you speak for 30 seconds in a loud voice, you are going to project aerosol more than six feet in the direction of your interlocutor.”
The researchers hope the findings will highlight the importance of ventilation and face masks to reduce the spread of coronavirus. Dr Stone added: “It certainly highlights the importance of ventilation. Especially if you have an extended conversation.
"Masks really cut this flow of tremendously. This identifies why (most) masks play a big role. They cut everything off."