From Opera Wire: The Metropolitan Opera Orchestra participated in a Princeton University study that indicated surprising findings about air flow in trained opera singers. The orchestra opted to do the study as a means of actively pursuing ways to get back to work safely. 
https://operawire.com/metropolitan-opera-orchestra-participates-in-princeton-university-study-about-air-flow/

Related from Met Orchestra Musicians: MET Orchestra / Princeton University Study Indicates Surprising Findings About Air Flow In Trained Opera Singers