For the last two decades, I’ve sat in the middle of the clarinet section of orchestras, oblivious to the possibility of microbes swirling around me amidst the melodies and harmonies that fill the air. I didn’t once think about the potential spread of pathogens from another player’s instrument. That is, not until the COVID-19 pandemic hit.
There have been few anecdotal cases of infectious disease transmission in the orchestral setting and we know little about how air travels when it leaves wind instruments. But during the COVID-19 pandemic, aerosol researchers and eager orchestras teamed up to determine one thing: can orchestras, particularly the wind section, perform safely during the COVID-19 pandemic?
University of Minnesota x Minnesota Orchestra: Aerosols rise upwards due to thermal plumes and drop to background levels a foot away
Last year, researchers led by associate professor Jiarong Hong from the University of Minnesota worked with the Minnesota Orchestra to investigate aerosols generated from wind instruments. In their study, they first quantified aerosols that traveled out of the different instruments. Tubas produced the fewest aerosols, less than what a person would emit breathing. The worst culprit? Trumpets (I’m reminded of all the times I’ve sat directly in front of the trumpet section). My personal favorite, the clarinet, produced an amount of aerosols similar to that from breathing and speaking, and their emission patterns really depended on the player. The scientists also saw a different aerosol output depending on the articulation patterns of the music: sharp staccatos and smooth slurs of phrases resulted in different aerosol patterns.
In a follow up study not yet published, they found that most aerosols traveling through wind instruments don’t make their way farther than a foot away horizontally due to air flow from the instrument itself. Less than 10% of the aerosols could be detected from 4 inches away compared to the source and the scientists could not detect aerosol flow a foot away beyond background levels. Over a foot away, any aerosol transport depends on the ventilation in the room, not the instrument. What’s more, two layer “masks” wrapped around the instruments’ bells of the instruments blocked 75% of the aerosols emitted.
The lab’s latest studies focus on how to mitigate aerosols based on their flow patterns. They noticed that many aerosols spread upwards rather than horizontally due to the human thermal plume effect. The team is using their findings to develop the optimal placement for filters to capture aerosols and the best social distancing practices between players.
Photographing aerosol spread with the Vienna Philharmonic
Across the Atlantic, the Vienna Philharmonic Orchestra resumed rehearsals and performances after their own aerosol dispersal study. In their experiment, the musicians wore devices that produced aerosols as they breathe into their instruments. Photographing the musicians playing in front of a dark screen captured the aerosols drifting around them, though not as quantitative as the above study. With regular testing, distancing, and masking, the orchestra got the green light to rehearse and perform. To learn more about this study and other ways orchestras are developing to get together safely, head over to Eva Amsen’s article.
We intended to follow a positive and constructive path by conducting a scientific experiment using “Aerosol”. The results of said experiment were made available to the Austrian Ministry of Health and the public.
Further info: https://t.co/nWV6rL0KV0 pic.twitter.com/KctFrZwyCk— Vienna Philharmonic (@Vienna_Phil) May 18, 2020
Microbes deposited on instruments
Though these might be the first experiments on aerosols emitted from instruments, the question of instruments as sources of infections date back to the 1950s. Then, two groups of researchers found that brushing and rinsing mouthpieces with sanitizer or detergent solutions could reduce the number of microbes on the mouthpieces of instruments. In 2011, the late Stuart Levy and his lab examined previously played wind instruments – clarinets, flutes, saxophones, and trumpets in their quest to find microbial growth. All of these instruments had viable bacteria, mold, or yeast. Instruments that were played within the past three days had more bacteria common in the oral microbiome. And not surprisingly, new reeds had fewer bacteria than stored reeds and yeasts and molds predominated especially during long-term storage.
I’d love to hear from my musicians in the audience. Have you ever thought about the microbes on the surfaces of your instrument or channeling microbes into the air through them?
References
Aerosol generation from different wind instruments – Research study from the University of Minnesota covering aerosols from instruments. Now published in the Journal of Aerosol Science.
Flow Field Imaging Lab YouTube channel
Risk assessment of airborne transmission of COVID-19 during orchestra performance – Research study from the University of Minnesota on flow patterns and “masking” instruments
