Re: How do hover flies hover noiselessly ?

I don't know!

Here are my thoughts though:

Because we can't hear them doesn't make them 'noiseless'.

A noise is usually annoying sound. I am sure that they make some sound, but it is not audible to human ears.

The question as to why it would be beneficial for some flies to make audible sound while flying whilst these don't is interesting but perhaps not necessarily valid. The sound they make my simply be a byproduct of their behaviour and flying needs.

It may be that they have only one pair of wings verses the two pairs of other flies?

Again... sorry... I don't know the answer to your question. Good luck