Speculatively, humming might be effective against infections via increasing nitric oxide concentrations in the nose: https://www.lesswrong.com/posts/NBZvpcBx4ewqkdCdT/do-you-believe-in-hundred-dollar-bills-lying-on-the-ground-1

403 Forbidden

In a year, will I believe humming is effective against respiratory infections?

I won’t trade on this market. I have no medical background and will likely defer to a whatever consensus will exist at the time.