This requires either a low noise sensitivity or a willingness to replace fans every year or so. I've put a ton of research and work into building silent PCs over the years. They inevitably start out silent, but as the fans wear they become audible around the year mark and annoying around the two year mark.

Honestly I find people claiming something is "inaudible" or "not audible" on the internet extremely dubious, because every time I buy some cooler that people claim is "inaudible", I find it very audible. Either I have good ears, or people have very bad ears or loud environments. I assume in many of these cases people simply live in loud cities and have lost any feeling for what the word quiet means and regard PC fans whirling around at 20-25 dBA as quiet.

And in any case, with air cooling and components that aren't bottom-of-the-barrel, the quiet part ceases as soon as load is applied anyway. But that's what I'm here for, so a PC that's only quiet as long as I don't use it - pointless.

I have a standard computer without an extra video card (only the one on the MB) that I use as my main server running 30 services or so on docker.

It sits in the living room and I honestly do not hear it ever, except when it starts to vibrate for some reason sometimes (I will hunt that down someday)

This includes the time I slept a few times on the couch that is just next to it and I was annoyed by a small wall clock 5 meters away (I took the battery off and it is 11:15-ish now for 2 or 3 years, nobody noticed I think)

So that really may happen.

EDIT : I just checked and the clock is still off :)