If you’re debating whether to wear a mask in public, consider this. A new study suggests that simply talking can be one of the main ways this coronavirus is spread.

Researchers from the NIH and the University of Pennsylvania used a sheet of laser light to visualize bursts of speech droplets produced during repeated spoken phrases. They found that loud speech can emit thousands of oral fluid droplets a second. It takes between 8 and 14 minutes for those droplets to go away.

The study was conducted in a closed environment with stagnant air. We don’t know the spread or duration of these speech droplets in better ventilated environments. But it does show the risk of an infected person – even someone who doesn’t know he or she has COVID-19 – can spread it to others just by talking to them from a few feet away.

If you want to go out in public, you might wear a mask in closed environments with many people in them, like grocery stores. Even wear a mask in a restaurant until it’s time to eat. Or better yet, stick to outdoor environments whenever possible.