Central Controlled Residential Ventilation: Supply and Exhaust Air, Door Bottom Gap

There are also soundproof overflow solutions, e.g. in the form of special dropping seals.

Are/were there any problems with the noise level of the supply air for anyone?

Assuming the supply air for the system in the technical room is not "far" from the outdoor unit of the air-to-water heat pump, does the noise then "come into the house"?

Assuming the supply air for the system in the technical room is not "far" from the outdoor unit of the air-water heat pump, does the noise then come "into the house"?

No, we have the fresh air intake above the outdoor unit of the heat pump. There are no problems. In the main air duct, behind the central unit, there is a silencer, so that nothing can be heard at the respective supply air outlets in the rooms (to our ears). I find the central unit itself loud, but outside the utility room it is not perceptible (we have a soundproof door with a drop seal, I don't know how it would be without).

There are also soundproof overflow solutions, e.g. in the form of special drop seals.

Soundproof is also airtight, so the Schallex seal should only be used in certain rooms.

And 8mm gap sorry you can see everything underneath.

Soundproof also means airtight

No, as long as we are talking about the audible, practically relevant range. It is precisely leakage elements with effective sound insulation (Planet Mine-S as an example).

Thank you very much for the clarification, they have a wide variety of variations. Anyone who still voluntarily allows an 8mm gap as overflow is either deaf or doesn't know any alternative.