Hard times for the ‘brass’, in a pandemic. After several studies – and even episodes of outbreaks within famous choirs and ensembles – have highlighted a greater risk of Covid infection among the professional ‘uvula’, wind instruments have also ended up among the suspects, as potential ‘super spreader ‘, and the orchestras had to reorganize themselves according to a’ virus free ‘logic, addressing one particular concern: are trumpets, horns, saxophones, clarinets vectors of contamination through the dispersion of aerosols? Science today breaks a lance in their favor. A team of scientists from the University of Pennsylvania worked with musicians from the Philadelphia Orchestra to try to figure out how much aerosol is produced and dispersed (how far) from wind instruments. Tracing the path with the help of the laser, the authors came to a conclusion: “We were surprised that the amount of aerosol produced” with the wind instruments “is in the same range as normal speech,” explains Paulo Arratia. of the University of Pennsylvania, author of the study published in ‘Physics of Fluids’. “I was expecting much higher flow rates and aerosol concentrations.” Experts characterized the flow and laser-tracked the mist particles emitted into the air; they also measured the concentration of aerosols from wind instruments – such as the tuba played by musician Carol Jantsch – with a particle counter. Then they combined these two measurements and developed an equation to describe the dispersion of the aerosol, where the velocity of the aerosol decreases with distance from the instrument. The idea was to help determine the distance traveled by the aerosols by measuring the velocity of the outflow. Result: the aerosols emitted by the wind instruments shared a concentration and a distribution of dimensions comparable to the normal vocal and respiratory ‘events’. In other words: playing the trumpet or speaking makes no difference in terms of aerosol dispersion. And, indeed, a sneeze is worse. The one faced by scientists may appear to a casual glance to be a minor problem. But in reality, the impact of Covid-19 in the world of music was significant: during the pandemic many live events and music festivals were postponed and canceled to protect the public and musicians. When the performances were resumed, many groups had to adapt repertoires, favoring for example the strings, to modify the number of musicians and their positions – in particular the winds – in the auditorium. “Ideally, the musicians would sit next to each other to bring the best sound to life, but such an arrangement became a problem during the pandemic,” Arratia points out. In the study, flow measurements showed that the velocities of the jet exiting the wind instruments are much lower than those of coughing and sneezing episodes. For most instruments, the maximum decay length of the emitted particle stream is less than 2 meters from the instrument opening. Consequently, the authors conclude, musicians who play wind instruments should stay 6 feet away (about 1.8 meters), as is generally recommended for people to limit the risk of contagion. The researchers will now examine contamination through aerosol dispersion from a ‘collective’ point of view, to understand how much aerosol and flow are produced by the entire orchestra playing together. “It is hoped – concludes Arratia – that this work will guide health officials to develop protocols for live and safe musical events”.
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