In view of the spreading of the Covid-19 virus, Real-Time Background Oriented Schlieren (RT-BOS) and backlight scatter imaging were used to visualize the air motion and droplets during talking, coughing, sneezing, singing, playing wind instruments. The effectiveness of personal protection like face masks and shields were studied. The distance of air (aerosols) spreading depends on the diameter/shape of the opening and air volume blown out per unit of time. Remarkably, the aerosol and droplet spreading of singing is similar or less than talking and even less for wind instruments. Any mouth mask although leaking air is effective in preventing droplets to spread.
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