"We have studied the amount of particles we actually emit when we sing -- and by extension -- whether we contribute to the increased spread of Covid-19 by singing," said the study authors from Lund University (LU) in Sweden.
There are many reports about the spreading of Covid-19 in connection with choirs singing. Therefore, different restrictions have been introduced all over the world to make singing safer.
"So far, however, there has been no scientific investigation of the number of aerosol particles and larger droplets that we actually exhale when we sing," said study researcher Jakob Londahl of LU.
For the study, published in the journal Aerosol Science and Technology, 12 healthy singers and two people with confirmed Covid-19 took part in a research project. Seven of the participants were professional opera singers.
"Some droplets are so large that they only move a few decimetres from the mouth before they fall, whereas others are smaller and may continue to hover for minutes," said study researcher Malin Alsved.
"In particular, the enunciation of consonants releases very large droplets and the letters B and P stand out as the biggest aerosol spreaders," Alsved added.
During the research experiments, the singers had to wear clean air suits and enter a specially built chamber supplied with filtered, particle-free air.
In the chamber, the analysis was conducted of the number and mass of particles emitted by singers during breathing, talking, different types of singing and singing with a face mask.
During the song tests, aerosols and larger droplets were measured using strong lamps, a high-speed camera and an instrument that can measure very small particles.
The louder and more powerful the song, the greater the concentration of aerosols and droplets.
"We also carried out measurements of virus in the air close to two people who sang when they had Covid-19," the team wrote.
Their air samples contained no detectable amount of virus, but the viral load can vary in different parts of the airways and between different people.
"Accordingly, aerosols from a person with Covid-19 may still entail a risk of infection when singing," the team notes.