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

I was in a model home from Viebrockhaus, there was a heat pump inside that does not need an outdoor unit. I actually did not hear the heat pump, except in the utility room,

If you pay attention to this in a model home, please ask whether they have installed extra sound insulation in the model home or used thicker walls!!! The thickness of the walls can also be seen by yourself at the door frame. If yes, then ask whether this is included in the standard price or if there is an additional charge.

maybe a solid core door is enough

The first measure would be, in my opinion, a drop seal; only after that would I replace the door leaf (or both together, but never a heavy door leaf without a drop seal). We are getting a Planet Min E/F (link on request, but easy to find), which promises sound insulation and pressure relief. Let's see ...

Decoupling absolutely important (and often neglected)

Correct (I fear both statements are correct)!

Which heat pump is installed at your place?

Flexotherm 87/4

I can understand the original poster well. I will also have to deal with the problem of noise sensitivity (especially when you want to sleep) in due course. How sensible would the idea be in this context to relocate the [Technik/Heizungsraum] to, for example, an extended garage? Or is that nonsense because in that case all the lines have to go over to the house (additional costs, heat loss, etc.)?