Malcolm Smith wrote:
A brass playing friend of mine showed me this informative video:
Sound waves in Brass instrumentshttps://www.youtube.com/watch?v=xyoGz5PSuSw
Spread that! :clap:
But he still also stretched a (huge!) "mask" across the bell of his sousaphone as a joke and to allay uneducated people's fears now that he's out performing in street bands again.
I apologize for the following long post, but I see this discussion leading to a false sense of security and possible harm to folks on this forum and others. One part of my day job is Covid-19 prevention and I would like to share some of the information I have gathered in hopes that it may reduce this potential harm.
This video is highly misleading. It creates a "straw man" false concept that the SARS-CoV-2 virus is transmitted at speed of sound from the trumpet bell (or singer's mouth) to the listener's breathing zone. Then it demolishes this admittedly ridiculous concept using common sense. Fine, so we get that this somehow magical concept of delivery of the virus to a person a long distance away from the musician is not consistent with the theory of sound wave propagation in air.
But that is not, and never has been, the problem with risk of virus transmission by vocal or brass instrument performance in public. The problem is the potential for short distance spread of the virus by what is called the airborne route. This is a route of transmission of viruses by very small particles mostly less than 5 micrometers in diameter, and is believed to be a major contributor to the spread of tuberculosis, chicken pox and measles. Whether it is a major or minor contributor to spread of SARS-CoV-2 is currently a raging controversy in medicine, epidemiology and fluid mechanics, with many economic, social and political factors underlying the scientific discussions.
Airborne spread can occur when these microscopic particles slowly float around for minutes or hours in the indoor space and may be inhaled or innoculate the eyes or mucus membranes of others in the space close to the infected person. It can also occur when an infected person coughs or sneezes and emits a turbulent buoyant cloud of particles that can propagate across a longer distance (up to 26 feet has been reported) similar to (but faster than) a smoke ring floating and drifting across a room from the mouth of the smoker who blows the smoke ring. One study reported that the particles can remain airborne for up to 3 hours but stopped measuring at that time and does not reassure us that longer times are not possible or likely. Vibrating lips, vocal cords and reeds are quite effective in generating these small particles.https://journals.plos.org/plosone/artic ... ne.0020086
A published case report of an outbreak of SARS-CoV-2 infection caused by 2 chorus rehearsals in Skagit County, Washington State, USA clearly demonstrates the potential for "superspreading" to occur when one or more infected individuals sings in an indoor enclosed space without a facemask. The setting was a 2.5 hour choir rehearsal with one known symptomatic index case and possibly other presymptomatic index cases in the 1-3 days they could be infectious before symptoms began. As a result of that one choir rehearsal, from 53% to 87% of the 61 participants became infected, and 2 of those died. A report of this "natural experiment" was published by the US CDC.https://www.cdc.gov/mmwr/volumes/69/wr/mm6919e6.htm
But these superspreading events are not the norm. Typically one infected person infects between 0.5 and 3 other people during the week or so that they remain infectious with SARS-CoV-2, not more than 30 people in a couple hours. These horrifying superspreading events are less common than they could be because we have learned from careful tracing and follow-up and reports of events like this to avoid going out when sick and to practice universal masking, hand hygiene, social distancing and avoidance of unmasked singing and talking in indoor congregate situations. These and other infection control behaviours have become the norm and all contribute to reducing transmission, but only if they are implemented, enforced and continue to be followed.
How is all this relevant to wind instruments? In a live performance situation the concern really does include "muso to muso" and muso to audience transmission, in addition to the audience to audience and audience to musician transmission that also may occur. We need to always be aware that the infection can be transmitted in the 1 to 3 days prior to onset of symptoms, or even if symptoms never occur. An infected singer or horn player can thus be a hidden source of infection that needs to be controlled during live performances and rehearsals. Masking and distancing between musicians will reduce the chances of this a lot, but obviously these approaches are not feasible for singers or horn players. Currently available information does not completely reassure us that airborne transmission is not occurring.
We don't yet have a good answer for this. Medical testing can miss infected cases and daily testing, which is used for movie/tv actors, is not economically feasible at this time. Masking the bell might work for a trumpet or tuba but not for a saxophone, flute or other similar instruments that are not sealed tubes. Masking the player with a hole in the mask for the mouthpiece won't address this problem of possible airborne transmission. Singing with a mask on is not optimal. Live performances with good monitoring and adequate distances (probably 6 or 12 feet or more) between any 2 people (musicians, sound people and other employees), and live streaming to audiences at home may temporarily get the music industry through this pandemic, but may still allow rare cases of transmission and may be damaging to the experience of playing and listening to the music.