Ventilation system - Noise level dependent on which factors?

We are planning our 40+ single-family house with a LWW and a ventilation and exhaust system.

Some time ago, we visited a model house of a company that starts with Finger and ends with Haus (I don’t know if I’m allowed to mention the name). This model house was also equipped with a LWW and a ventilation and exhaust system. The air ducts for this were on the floor, both in the ground floor and in the upper floor. Downstairs, we already noticed the rather louder noise of the ventilation, but when we were upstairs in the closed meeting room, it was really disturbingly loud.

I can’t really describe it properly, it sounded like metal with air blowing through it. Really difficult to describe, but in any case, it was noticeable and unpleasant.

Another time, we were in a model house of a company with Streif Haus in the name and no little horn at the end. However, here it was a LLW with integrated ventilation. Here we absolutely didn’t hear anything, not even with the door closed and my head (almost) in the air outlet, which was on the wall.

Actually, we have never heard the air, not in any of the houses, noticeable noise was only in the first mentioned house.

Since we plan the same principle, albeit with different brands, I am now a bit afraid that it would be like that in our house as well, because then this system would be 100% off and permanently! That just won’t work, not only during sleep but in general.

Can you generally take certain things into account in advance to achieve a reduction of the “noise”?

Is the brand decisive?

Does the brand of the ventilation system also include the ducts or do they generally come from somewhere completely different, so that you might be lucky or unlucky depending on what the house builder installs?

I would be grateful for your answers…

Best regards
Dany250

Speculation ON:

When sheet metal air ducts are connected, air turbulences (possibly including vibrations) can occur at the joints (organ pipe principle) and cause disturbing noises.
However, it would be very unlikely for the same effect to occur in the other object using the same technique.

I would not be fundamentally worried if that were the case.
A firm punch on the joint can sometimes eliminate the "defect."

Even if fans and pipes are sold under the same label, they usually come from different manufacturers.

I don't know, it sounded the same throughout the whole house. I would support your theory if it were in individual rooms, but here it was both downstairs and upstairs in the house. And it wasn't a whistle, it was just a constant noise of tinny wind in a shaft (I wish I could explain it better).

Since there isn't much feedback here, I hope it's because the problems rarely occur, which is a little bit reassuring :).

Well, if you value volume, you first have to choose a high-quality ventilation unit and secondly implement a generous design of the air ducts, etc. Provide sufficiently large duct cross-sections or lay several air ducts to the supply and exhaust air openings with high volume flow. Avoid too long air duct lengths, and very importantly, proper measurement adjustment where at least one of the throttles remains completely open. Whoever botches it from the start will find it hard to fix later...

And if you are very sensitive, install two silencers in series after the system. Also important, the large ventilation ducts to the outdoor air and exhaust air from the controlled residential ventilation system should be kept as short as possible. And then plan for an enthalpy exchanger (or at least be able to switch to one later), then it is really comfortable.

Decentralized systems are generally also loud compared to a central variant.

Otherwise, yes, the manufacturer is also crucial, as they build the devices and fans are inside. The geometry of the blades alone determines how loud it will be afterwards.

Maybe it was only "loud" in that one house because the system was undersized and/or set very high. It’s not supposed to feel stuffy in the dense model home construction, and the great indoor climate is always advertised - so proper ventilation isn’t a bad idea.

Otherwise, one should not avoid silencers (of whatever type) in the system. Central is significantly better than decentralized. Systems with tree/star topology are preferred, nothing that distributes air in series (telephone noise across rooms).
The air volume flow should be a maximum of 50% of the device’s possible capacity at nominal ventilation. This makes the fan run slowly and therefore quieter; manufacturers publish nice diagrams about this.
Pipe diameters should not be undersized.
The system should be planned according to where which flow rate is required. In rooms with higher demands, it is preferable to install two valves instead of one with increased flow. If that is not possible, this one valve should at least be connected doubly, rather than forcing increased flow through one pipe.