Countless concerts and festivals were postponed and canceled in the early days of the coronavirus pandemic. Events later took place again, but mostly with a limited number of spectators. In order to protect both the audience and the artists from infection in the best possible way, careful consideration was also given to how the musicians should be distributed on stage; and sometimes even changed the repertoire to use more strings than winds.
A research team from the University of Pennsylvania, together with the Philadelphia Orchestra – a Pennsylvania symphony orchestra founded in 1900 – investigated how many aerosols actually produced by wind instruments and distributed in the area. The results were in the journal “Physics of Fluids” released.
Aerosols behave similarly to speaking
The researchers used visualizations to describe the flow escaping from the orchestra’s wind instruments, such as a tuba. Then they tracked the particles with a laser. They also measured the aerosol concentration with a particle counter. These two measurements were then combined to calculate the extent to which aerosol velocity decreases with increasing distance from the instrument.
The surprising result: aerosols emitted by wind instruments have a similar concentration and size distribution as aerosols emitted during normal speaking and breathing. The flow measurements also showed that the speed at which the aerosols exit the instrument is much lower than the exit speeds when coughing or sneezing.
Two meters distance is sufficient
“Ideally, musicians sit next to each other when composing and making music – this became a problem during the coronavirus pandemic,” says the author of the study Paulo Arratia, Professor in the Department of Engineering at the University of Pennsylvania. “But we were surprised that the amount of aerosol produced by wind instruments is in the same range as that of normal speech.”
He had “expected much higher flow velocities and aerosol concentrations”. The aerosol distribution does not extend further than two meters – measured from the opening of the instrument. As a result, musicians who play wind instruments should keep a distance of about two meters – or as one would say in Austria: the length of a baby elephant – on stage.
Next, the research team wants to investigate which aerosol concentration and propagation speed is generated by the interaction of the entire orchestra. Study author Arratia hopes that health authorities will include this in future guidelines for the safe implementation of concerts and festivals.