My Fixie is about as silent as I can imagine any bike ever being, it did have a creak that seemed to reverberate through the frame for one day, a couple of weeks ago but I traced that to the Seat post, tightened up the rail clamp and it’s as quiet as a very, very quiet thing again…
My SS MTB isn’t bad, but it’s only when you get on that road fixie and all you really hear is tyres on tarmac that you realise just how many little noises you filter out, freewheel, cable outers tinging on tubes, the odd chain rattle…
My 2×9 Geared HT and my DH bike both sound like a bag of spanners, which is fine, unless I start to get a rubbing rotor or a mystery creak, then it just drives me up the wall until I can trace and cure the cause.