How scientific study of spit, airflow helped Utah Symphony open its season

SALT LAKE CITY — Playing wind instruments as part of an ensemble in the middle of the COVID-19 pandemic is inherently risky, especially if done in front of a live audience.

After all, a musician must forcibly blow through one end of their instrument and out the other to produce sound, which could potentially spread the virus.

Because of this, many orchestras across the county have canceled their 2020 seasons. But the Utah Symphony and Utah Opera weren’t ready to throw in the towel and instead looked to science and engineering for ways they could best mitigate risk while still holding live performances.

James Sutherland and Tony Saad — two professors of chemical engineering at the University of Utah — were asked to do something unique and recommend risk-mitigating techniques for wind instruments based on airflow patterns in both Abravanel Hall and the Capitol Theatre in Salt Lake City, where the symphony and opera perform.

“We’re not saying anything about whether a person is going to be infected or not. Obviously if you reduce the accumulation of droplets, in tandem, you’re going to reduce the possibility of someone being infected. But that’s not a judgment call we can make,” Saad said.

“But our solution has reduced concentration accumulation by a factor of 10 to 100, depending on what location you look at on the stage.”

The researchers’ primary goal was to find ways to funnel respiratory droplets produced by woodwind and brass musicians toward exits and away from audience members and other players in the orchestra.

To do this, they used a technique called computational fluid dynamics to analyze the different performance venues, allowing them to understand in “tremendous detail” how fluid moves in different conditions, according to Saad.

“Once you have an understanding of the flow itself — the flow dynamics — on a computer, then you can make judgment calls on what’s going on with the airflow, what you can do to change the airflow,” Saad said. “In addition, as you are calculating the airflow, you can also calculate how things move around in the airflow.”

Using data collected from previous literature, the scientists know the concentration of respiratory droplets produced by each instrument and at what speed they move. That data, coupled with the calculated airflow, gives the engineers an idea of how droplets move around a given space.

The mathematical equations used to compute computational fluid dynamics are highly complex and can’t be done by hand. Instead, the researchers used numerous computers, and the process still took around 500,000 combined hours to finish, according to Sutherland.

“So if you had just one computer working on this problem, it would take you around 50 years to generate all the results,” he said. “It gives us a very detailed view of ... the fluid flow on the stage, where the flow is coming from, where is it going. As emissions are introduced to the stage area, we can track where those go, where they accumulate and where they are pulled out.”

Switching seats

With this knowledge, the researchers suggested making several temporary adjustments to the performing hall during events as well as shifting musicians around to best direct their emissions toward exit points.

“Our final mitigation ideas were let’s open up any doors or any openings that exist in the concert halls — on the stage — let’s open up any doors, windows, whatever is available to clear as much air as we can,” Saad said. “And let’s also potentially move these emitters, the instruments that are emitting droplets, closer to those vents.”

Typical orchestras have percussion to the back, with brass, woodwinds and strings toward the front. However, what makes for the best acoustic arrangements doesn’t always align with what’s best for preventing the spread of disease.

“In Abravanel Hall in particular, that arrangement was a bit problematic, because we generally move air toward the vents which are along the back, at the floor level, along the back and the sides. What that means is that the brass and the woodwinds, which are kind of center stage, are emitting things that are getting carried across their neighbors,” Sutherland said.

“As we saw that, we thought, ‘OK, this is just not going to work.’”

For Abravanel Hall’s altered performances, the engineers suggested that percussion take center stage, brass move toward the back and woodwinds move toward the back and sides.

“By doing that, we basically allowed all of these instruments that are emitting aerosols and droplets to have those emissions trained in the flow that’s going right out the vents that they’re sitting next to or out the doors they’re sitting next to,” Sutherland said.

The researchers just finished their analysis of Capitol Theatre and said their suggestions for the venue will likely look much different than those for Abravanel Hall.

“The approach is the same, the considerations are the same, but the solutions — each venue is very unique, because the airflow patterns in the venue are unique. So the solutions that we proposed or recommended for Abravanel Hall look quite different than the solutions we’re suggesting for Capitol Theatre, because the difference in the HVAC system and the ventilation,” Sutherland said.

Scott G Winterton, Deseret News

While the opera will be performing in Capitol Theatre, the engineers were only asked to analyze the accompanying instruments, not the singers themselves, who will be sectioned off from the other musicians.

The researchers plan to present their suggestions Tuesday. Both warned, however, that their research is only part of the puzzle, and they are ultimately not the ones who decide when risk is too high to continue. The symphony has other experts advising them on matters of viral transmission.

Full orchestra?

For its part, the symphony, which has performed the last two weekends after an extended layoff, has followed the engineers’ advice. The first weekend, it had strings perform but added woodwinds, brass and percussion back in separate sectionals last week.

“We have absolutely been adhering to (the suggestions),” said Steven Brosvik, the president and CEO of the Utah Symphony and Utah Opera. “It has been useful already just in the fact that we have been able to have winds and brass on stage. We are taking everything we do in incremental steps and adjusting to what’s happening around us.”

Now that winds and brass have returned, it opens up the possibility of the full orchestra taking the stage together in the near future.

“The next step we hope to get to as soon as we can, and we feel like we’re ready, and everybody feels like we’re set, will be to have winds and brass mixed in with strings, so we can do a lot more of the standard orchestral repertoire,” Brosvik said.

He did not feel comfortable sharing a timeline, but he said the orchestra will continue to monitor and discuss the evolving situation in Utah.

The symphony, along with Salt Lake County Arts & Culture, which owns Abravanel Hall, is working with government officials and imposing other standard COVID-19 guidelines as well, including required social distancing and mask wearing for audience members.

Utah Symphony

“Arts & Culture venues are operating under modified event guidelines, allowing us to reopen the venues slowly and safely for performances,” Matthew Castillo, Salt Lake County Arts & Culture acting division director, said in a statement. “Audience capacities are limited to allow for social distancing of 6 feet between households in all seating areas. Patrons are required to wear face coverings during performances and each venue has enhanced cleaning and sanitizing procedures.”

If audience feedback is any indication of safety, the symphony has done a good job so far in its phased reopening.

“After our first week of audience surveying for guests who had been here for the concert, I think we were at 93% of our audience members checked the ‘extremely comfortable’ box on the survey,” Brosvik said.

The Utah Symphony will perform “Celebracion Sinfonica!” on Thursday, Friday and Saturday at Abravanel Hall. The symphony has not finalized plans to hold events past October, with the rest of the year pending discussions between government officials and other intra-organizational groups, Utah Symphony officials said.

The Utah Opera plans to open on Friday, Oct. 9, and will be performing a double bill: “The Human Voice” and “Gentleman’s Island,” at the Capitol Theatre. They will hold shows on various dates through Sunday, Oct. 18.

Utah Symphony