Close ventilation opening

How do you seal the ceiling breakthrough of the ventilation pipes (laid on the floor, concrete ceiling)? With concrete, screed? Do the pipes then need to be specially protected again?

Fixing those things with a sound decoupling killer is at least an original idea. Thanks for this humorous bedtime treat
Styrofoam, expanding foam & the like are seriously more recommended there.

Fixing those things with a sound decoupling killer is at least an original idea. Thanks for this humorous bedtime treat
Styrofoam, construction foam & the like are seriously more recommended.

Ok. Also for water pipes? Serious question, I asked several builders, the architect, and the shell builder and everyone says something different (so generally, how to close ceiling penetrations). Here the styrofoam would even still be inside (which was a placeholder in the precast concrete slab), the pipes were run through. However, the entire opening is much too large for the few pipes (approx. 20 x 50 cm). Can the styrofoam be left in there or does it have to be filled otherwise (because of sound from the technical room up into the bedroom)?

I actually wanted to fill our core drillings with expanding foam.

In ventilation ducts, air masses are moved, causing the ducts to resonate. Therefore, I would not couple them to other components into which they would transmit their vibrations. In the specific case, I assume that by "ducts" flat channels of a controlled residential ventilation system are meant, where the problem is less severe. Generally, the problem arises at component penetrations when different materials (= materials with different coefficients of expansion) are subject to temperature differences: where they are fixed against each other, compression/tension/rubbing points are created, and something placed in between first absorbs the temperature. So it is best to use something that is flexible or elastic, avoids smoldering fires, etc. Styrofoam is rigid, but on the other hand also dimensionally stable, and construction foam is suitable for the temperature (fluctuation) spectrum on exterior walls. Which of the experts provides the most plausible explanation for the approach they recommend?

Yes, these are flat ducts. I found the construction foam the most convincing (and the easiest to fill even the smallest gaps, and according to the description of a fire protection foam, the sound insulation is apparently also good, 59 dz), but the architect said that it would eventually crumble; he was in favor of Styrofoam (but he couldn't say how the sound insulation is in this case either). However, I find this difficult to apply without creating large gaps. The foam also states that it is suitable for gaps up to 40 mm. However, it would need to fill more. (By the way, the breakthrough is not near the exterior wall).

Would you leave the Styrofoam with the water pipes?