What’s the answer to orchestras returning safely in an age of covid-19? Seating people who play instruments with the highest aerosol output in the right place and getting the air flow right, according to a US team that modelled how concert halls could minimise players’ risk of infection.
“The performing arts have been hit really bad,” says one of the team, Tony Saad at the University of Utah. In the US alone, the fine and performing arts sector has lost an estimated $42.5 billion in sales. Globally, professional and community orchestras are still struggling to resume during the pandemic, due to challenges over social distancing and concerns over aerosols from wind instruments and singing.
Simply having all players uniformly seated two metres apart is not the answer, the team found after working with Abravanel Hall and the Capitol Theatre in Salt Lake City, Utah. “You could be 2 feet from someone and be perfectly safe, or 25 feet away and in a bad way,” says James Sutherland, also at the University of Utah.
Sutherland and colleagues took existing data on the volume and speed of aerosols emitted by different wind instruments and combined it with observations of the ventilation systems at the two venues to build a fluid dynamics model simulating how players’ emissions move around when an orchestra performs. Each venue was divided into million of cells in the simulation between 5 and 10 cubic centimetres in size.
The results show that having doors open to remove aerosols is crucial. The other key way to minimise risk is a seating plan placing the instruments with the highest and fastest aerosol release – trumpets, oboes and clarinets – at the back of the stage, near the return vents in the venues’ ventilation systems. “It’s all about the air flow. That’s critical,” says Saad.
String players are placed at the front and, assuming they are masked, pose a “negligible” risk compared to wind players, he adds. The assumptions made – including the unrealistic prospect of everyone playing all the time – make the modelling a worst case scenario, says Saad. Taking all the measures together, the steps can cut the probability of infection by a factor of 100, the team concluded.
There are some caveats: the study did not look at singers, all aerosols were considered the same size when in reality they would differ and the cells the team split the venues up into could be smaller to provide more detail. However, none should change the big picture, says Saad.
Adam Schwalje at the University of Iowa says, “There are many assumptions that must be made about aerosol production from wind instruments, but there is tremendous variability in how many aerosols are created by different performers on the same instrument.”
“These simulations show we can characterise risk and we can mitigate it,” says Sutherland. Both he and Saad hope their findings will help orchestras return safely. While some principles will be broadly applicable for orchestras anywhere, Saad says more detailed analysis on risk will require modelling for individual venues. But Schwalje says this type of air flow analysis is expensive and requires expertise that may not be available to all venues.
It also may not take into account all types of air flow, including an effect in which a player’s body heat can create an upward-moving plume that affects how aerosols spread, says Jiarong Hong at the University of Minnesota.
He adds that it may disrupt an orchestra’s usual way of working. “Musicians in an orchestral band are very sensitive to their positions with respect to others in the band. For example, trumpet players are always seated in the back and they get used to watching and listening to bassoon and oboe players in order to coordinate their playing.” Orchestral pieces are also usually composed with the seating arrangement in mind, with smaller, quieter woodwinds up front.
Journal reference: Science Advances, DOI: 10.1126/sciadv.abg4511
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