I hope this considered to be a biology question. How do hoverflies (Syrphidae) hover soundlessly? Why don't  their wings buzz? Thank you.

Hoverfiles do indeed make a noise when flying see:
https://www.deepdyve.com/lp/oxford-univ … ywJJfS435N

also see
http://www.highlightskids.com/science-q … s-bee-buzz