Which heating technology is suitable if one is sensitive to noise?

We have gas! On the ground floor! Only separated from the open living area by a room door! We don't hear it!

I add: we don't hear it in the open living area - definitely not in the utility room, where it is located ;)

Thanks!
So, a heat pump would generally be better than, for example, gas, but gas can also be quiet, and not every heat pump is automatically quiet? Got it! ;)

I was in a show house from Viebrockhaus, and there was a heat pump inside that doesn’t need an outdoor unit. I actually didn’t hear the heat pump, except in the utility room, and even there only very quietly. But usually, you hear such things much better when you’re alone, and not when someone is standing next to you asking expectantly, "So? Do you hear anything?" :D

Not all noises are equally bad either. Strangely, I find the sound of a dishwasher calming, whereas a loud refrigerator annoys me (I once had one that I could hear through a closed door from 10 meters away). So, I still don’t know whether a heating noise would bother me at all, but if it does, it would be really bad. I’m not good at tuning such things out.

Depending on the season, it is quite possible that the heating from Viebrockhaus was off :D

I would not rule that out, although it was only a few days ago, and it had snowed the day before.

The HAR and the door must be well constructed/soundproofed, then you won’t hear anything anymore... no matter what is inside...

To be fair, Viebrockhaus does make sure that the HWRs are arranged somewhat sensibly.