insufficient sound insulation of the interior walls

Hello everyone,

first of all, thank you very much for the previous answers and sorry that I’m only replying now. The reason is my daughter, who wanted to come into the world a little earlier than expected.

But now back to the topic.
My main concern is to find the cause of this (in my opinion) increased noise level and then find a solution for it. Of course, I could also tear out the walls again and have drywall installed, but to be honest, I bought a new house so I wouldn’t have to do something like that right away.

Were the pipes sound insulated?
Is the sound possibly transmitted through the ceiling? How is the ceiling constructed? Plasterboard? OSB panels? Joint between wall and ceiling? What kind of insulation is above the ceiling?

According to the company that carried out the sanitary installation, the pipes were insulated. Is there a difference between insulation and sound insulation? How can I check if the pipes were really insulated without having to tear out the entire walls again?
I can’t say exactly how the sound is transmitted. With my layman’s understanding, I would say that it is transmitted through the walls. But that’s just a guess.

Since I have already lived in aerated concrete walls (an aerated concrete wall is also a wall), I rather suspect a transmission of the noises through something.
What is behind the toilet? Is the knee wall raised by masonry? -> Resonance body?

Unfortunately, I can’t answer this question. We moved into the house when everything was finished. I can only say that the toilet is mounted on the wall. The cistern is concealed.

I have made a small sketch of the living situation; maybe it will help to better understand and get to the bottom of the cause. It is of course not very professional and does not correspond exactly to the real living situation, but it should be enough to gather initial clues about the cause.

The red lines represent the drain pipes, all leading to the downpipe. The room primarily affected by the noises is room 1. In room 2, you can hear very well how the water rushes down the downpipe. Since it is only used as an office, it’s not so bad. Room 1 is used as a bedroom, and there you can really hear everything. You can even hear the light switch being operated and the toilet paper being unrolled.

As already mentioned, my main concern is to find the cause first. Only then can I consider whether it is a construction defect or not.
I continue to hope for constructive contributions.

Thank you in advance for your help.

First of all, congratulations!

After I read along here and the plumbers were at our construction site last week, I asked them. We are currently building with Ytong.

They said there are still enough companies that install pipes that do not insulate the sound. We were advised, in addition to the insulating pipes, to have the pipes additionally wrapped by the drywall installer in the boxing.
We have already discussed this with our drywall installer as well.

But since you can almost hear the fleas cough at your place..... the sound might be transmitted through the ceiling.
How is it constructed?