Musical chairs game? Why changing seats reduces orchestral aerosols.

If the instrument is a person, the trumpet is a super spreader. When the trumpeter blows into the mouthpiece, a small respiratory droplet called an aerosol emerges from the musician’s mouth and sprays through a brass tube into the air.

If a musician may unknowingly spit out an infectious virus during a deadly pandemic, it poses a potential problem for the orchestra. And the trumpet is not the only musical health hazard.

“A wind instrument is like a machine that aerosolizes respiratory droplets,” said Tony Saad, a chemical engineer and computational fluid dynamics expert at the University of Utah.

A simple but radical change-the relocation of musicians-can significantly reduce the accumulation of aerosols on stage, Dr. Saad and his colleagues reported. With new researchWas published in Science Advances on Wednesday.

Work began last summer when the Utah Symphony Orchestra began to wonder if and how it could safely return to performance.

“They were looking for people who could provide some credible insight into mitigation strategies.” James Southerland, a chemical engineer at the University of Utah and co-author of the study, said.

Researchers created a detailed computer model of a symphony concert hall, focusing on the location of all vents and the speed of air flow through the HVAC system.

Next, I mapped the typical position of each musician. The Utah Symphony Orchestra, like most modern orchestras, placed musicians in a standard pattern, with strings in front of the stage, followed by woodwinds and brass (flute and oboe, bassoon and clarinet). Then trumpet and French horn. The trombone and percussion sections have been placed at the back of the stage.

To model the spread of aerosols during a concert, they Recent research It is led by Jiarong Hong, a mechanical engineer at the University of Minnesota. In collaboration with the Minnesota Orchestra, Dr. Hong and his colleagues measured the concentration and size of aerosol particles emitted from a variety of different wind instruments. (Of their findings: trumpet, bass trombone, and oboe pose the highest risk.)

With these parameters set, Dr. Saad and Dr. Sutherland used what is called computational fluid dynamics simulation to see how air and aerosols flow through the Utah Concert Hall when all musicians are playing. I modeled it.

The simulation revealed a complex pattern of airflow. In general, air flowed from the ceiling air inlet to the floor air inlet at the rear of the stage. However, it was found that two different vortices were formed in front of and behind the stage. “You can see these big areas recirculating like a big tornado,” said Dr. Saad.

Aerosols can get caught in these vortices, swirl around and around the stage, and accumulate over time.

The trumpet, which emitted a large, concentrated aerosol cloud, caused certain problems. As the instrument’s aerosol plumes moved towards the vents behind the stage, they passed directly through the percussionist’s breathing zone.

“We saw this and said,’OK, this is a big problem. We need to solve it,'” said Dr. Sutherland. “And with insights into how the flow works, he said,’Well, let’s move some of these devices.’ “

They knew the idea could be controversial. Orchestras have generally been arranged in the same way for decades for reasons that include both acoustics and tradition. “We asked them when they started the project.’What constraints do we need to tackle? Can we move people?'” Said Dr. Sutherland. “And they said,’I will do whatever I think I can do to mitigate the risk.'”

They moved the trumpet to the back of the stage, right next to the air return vent. He then suggested moving the other wind instrument from the center of the stage, closer to either the back air vent or the stage door, and opening it.

The team hoped that these moves would allow the aerosol to flow directly out of the concert hall without having to pass through the breathing zones of other musicians or get caught in a whirlpool on stage. “You want smokers to sit near the window,” said Dr. Saad. “That’s exactly what we were here.”

Finally, we moved the instruments that do not generate any aerosols (piano and percussion) to the center of the stage. Together, these tweaks reduced the average aerosol concentration in the musician’s breathing zone by a factor of 100, the researchers calculated.

The exact airflow pattern varies from venue to venue, but the general principles should apply everywhere, the team said. The orchestra can reduce the risk of aerosol diffusion by placing the most risky instruments near open doors and air outlets. (Researchers suggested that orchestras that couldn’t do their own computer modeling could put the fog machine on stage and track how the fog flows.)

Dr. Hong, who was not involved in Utah’s research, praised the modeling work. “It’s not easy to simulate the flow in an orchestra hall,” he said. “They did a beautiful job in characterizing the flow.”

But he wondered if moving musicians was a really practical solution. “We work closely with musicians and they don’t want to be reorganized,” he said. (But for the student band, I think it’s perfectly fine, “he said.”

Instead, he suggested another solution, just as unconventional. It’s a mask for musical instruments. To Recent research, He found that covering the trumpet bell with a single layer of acoustic fabric could reduce particle emission by about 60 percent without compromising sound quality.

The Utah Symphony Orchestra, as part of it, proved to be open to rethinking its seats. And when I went up to the stage last fall, I went up to the stage with the stage door open and the wind instrument behind me.

“It was a big challenge for musicians,” said Stephen Brosvic, president and chief executive officer of the Utah Symphony Orchestra and Utah Opera. “But they all jumped into it and said,’Let’s go, let’s do it.'”

It will take weeks for musicians to get used to the new arrangements and will return to their traditional seating arrangements this fall, Brosvic said. But the simulation reassured the musician and made it possible to return to the stage, he said: “For us, it was life-changing.”

Researchers were pleased that the musicians were willing to accept the anomalous solution, but their findings could have been more damaging than other instrumentalists. As Dr. Sutherland said, “I had to apologize to the trumpet in advance.”