A new method for visualizing breath that is exhaled while someone is speaking or singing could provide important new insights into how diseases such as COVID-19 spread and the effectiveness of face masks.

«Scientists believe the SARS-CoV-2 virus is primarily spread through respiratory droplets that can be carried in the breath or expelled through coughing or sneezing,» said Thomas Moore from Rollins College, who performed the research. «But it is also transmitted by airborne aerosols, which are small particles that remain in the air longer than the larger droplets. The system I developed provides a way to estimate how far the breath travels before being dispersed into the surrounding air and can provide visual evidence that masks significantly limit the distance the breath travels in the air.»

In The Optical Society (OSA) journal Applied Optics, Moore describes how he used a variation of electronic speckle pattern interferometry to image temperature differences between exhaled breath and the surrounding air. The new technique can also be used to study the details of how breath flows from the mouth while speaking or singing, which could be useful for music instruction and speech therapy.

From musical instruments to people

Moore originally developed the imaging technology to study the flow of air through musical instruments such as organ pipes. «In response to the COVID-19 pandemic, I began imaging the breath of people speaking and singing,» he said. «I realized that by scaling up my existing system, I could likely determine how far the breath extends and how effective masks may be in limiting the extent of the breath.»

Most existing approaches used to image exhaled breath require expensive equipment and can image only a relatively small area. Moore designed a system that uses common commercially available optical components to overcome these limitations.

Story Source: Materials provided by The Optical Society. Note: Content may be edited for style and length.