Controlled residential ventilation - You can hear every word in the other room - Is this normal?

Did you have to cheer up the silencers or are they usually included?

There is the model "Auspuff" about one meter long. So-called telephony silencers. They are made exactly for this purpose and go directly into the supply and exhaust air duct and then work for all rooms. Alternatively, there are also soundproofed distribution boxes and I even think there is decentralized soundproofing on the valves.

With us, the soundproofed distribution boxes have been planned by the manufacturer from the beginning.

I find it quite strange that conversations from supply air rooms can be heard in exhaust air rooms. The common connection point of these rooms goes back to the ventilation unit.

That is the case with all pipes; all pipes run individually from the technical room into each individual room, whether supply air or exhaust air.
I don't understand at all why voices can be heard from the openings, as there is no connection between the rooms up to the ventilation system, and sound attenuators are installed there.

Best regards
Sabine

That's exactly what I've been asking myself the whole time ...

It depends on how the piping looks. There are actually more possibilities than the generally known ones from the collection box in the [HAR] to the rooms.

Are there any photos?

This is the case with all pipes, all pipes go individually from the technical room into each individual room, whether supply air or exhaust air.
I don’t understand at all why voices can be heard from the openings, there is no connection between the rooms up to the ventilation system and sound attenuators are installed there.

Best regards
Sabine

Not all systems go individually into each room. There are also sub-distributions etc.

Still strange, because supply air is spoken into here and exhaust air is heard. These are only connected to each other via the heat exchanger in the ventilation unit.

So apart from the suspicion that sound attenuators are missing, mixed-up connections also come to mind.