When it comes to COVID-19, some activities are riskier than others. Hiking alone in the mountains is pretty safe. Joining 100 other people to blow spit and air through instruments … er, playing in a symphony ... might be a problem. A team at the University of Utah led by scientists Tony Saad and James Sutherland recently completed a study of Abravanel Hall’s airflow to help identify risk for musicians in the Utah Symphony.
This interview has been edited for length and clarity.
Caroline Ballard: You are both chemical engineers, but you also both have some background in music, right?
Tony Saad: Yes, I studied classical guitar.
James Sutherland: And I'm a member of the Tabernacle Choir at Temple Square. We've been on hiatus since March due to COVID, so this project has been kind of near and dear to my heart as we try to get the performing arts back to performing in some way or another.
CB: We're told large gatherings are problematic because of COVID-19. Can you explain why?
JS: The more people you have in a confined space, the more likelihood that somebody may be infected. And that's particularly problematic when people are singing loudly or playing wind instruments where there's a lot of aerosolized emissions that can carry viral particles on them. The big difference of course with the orchestra is you don't have the ability to mask a wind instrument [player] like you would a string player, because they need to blow through their instrument.
TS: So our analysis was aiming to understand how these respiratory droplets move around on the orchestra stage.
CB: You modeled the airflow in Abravanel Hall and created an animation of it, which I've watched. And I have to say wow, first off. And second, it's a lot of spit droplets coming out of instruments and sort of swirling around into the air. Can you explain what's happening?
JS: Each instrumentalist and instrument emit different numbers of particles, different sizes of particles. And so we did our best to try to address that and capture that in these simulations. Where those particles go is strongly influenced by the local airflow patterns on the stage, and that's really dictated by the ventilation system. And then looking at how we might mitigate risk by moving instruments to improve the capture of these droplets by the airflow system out of the stage area.
CB: What recommendations did you come up with for the Utah Symphony?
TS: The easiest [option] was to manipulate the air conditioning system, and the recommendation there was to slightly over-pressurize the chamber and open the doors on the stage left and stage right. So that led to some of the air just moving out. But it wasn't enough. The next strategy was, we thought, what if we rearrange instrument clusters?
JS: We ended up moving the percussion a little bit toward the center of the stage. They were masked. So we actually moved the brass. In Abravanel Hall, there are vents located right at the back of the stage. And by moving the brass there, we could take the emissions from the brass instruments and pull it right out at the stage area through the ventilation system. And similarly, with flutes, clarinets, bassoons — we moved them near doors or near vents, and doing that really allowed us to reduce the risk to all of the players significantly — factors of maybe 10 to 100 reduction in exposure risk.
TS: Think of it this way. Suppose you're trying to transport a person who is smoking in your car. What would you do? You would open the windows to try to get that smoke as fast as possible, and you'd probably ask them to sit closer to the window. This is similar to what we did here.
CB: And I have to say — as someone who has performed in symphonies and choirs myself — rearranging is kind of a big deal. How did they take it when you proposed that as one of the solutions?
JS: The topic of rearranging orchestra members came up early in our discussion with the Utah Symphony leadership. We approached them and said, is this something that is on the table? And they said, you guys give us your best recommendations and we are happy to consider any of those that reduce risk.
CB: And the result of this is basically that the symphony wants to get back to playing regularly or more regularly. How has this project impacted that?
TS: The current setting, they're using only strings, and that was planned before we embarked on this project. But now with the data and the analysis that we're providing them, they are actually entertaining new pieces that will contain winds. So that remains to be seen. Although when we were invited for the final touches rehearsal, we noticed that they had the doors open and that was very — it gave me a warm, fuzzy feeling in my heart.
