@happyborg Mobile app called Spectroid is useful when trying to figure out what devices make most of the noise. It shows audio spectrum visualization that makes it easier to see what audio frequencies are loudest. Could also be useful for comparing how much better sound insulation improves things, or for comparing different kind of cooling fans.

@autiomaa thanks. Unexpected answer but yes, why not. Very useful to know. I'm up for hearing about anything home-labbers (is there a better term? ) find handy.

@happyborg Point is, a lot of people don't run their own home servers because those make too much noise. When trying to make things useful for small homes, noise levels matter a lot to keep people healthy. Extra noise reduces sleep quality and is also a reason why many got rid of their homelabs.