Hello,
so the BT has relented and partially decoupled the staircase from the outside and closed the supply shafts that were open. Unfortunately, this has brought no success.
Yesterday, the neighbor drilled a hole in the wall from outside. At first, there was a normal drilling noise at the spot where he drilled. Then temporarily nothing, and then the noise suddenly came from the chimney/stove area. Even very, very clearly. We will tell him this again. But I think the problem lies somewhere else. Simply no attention was paid to soundproofing; it was built as if it were a semi-detached house or something similar.
What has now become a very big problem, however, is the adjacent street or rather the low-frequency tones from the trucks. Unfortunately, the roof was planned incorrectly, far too light. Only about 20 cm of rock wool and above that just normal battens and concrete shingles. At the foot purlin is only a thin board and also a bunch of slots. In addition, there is a cavity between the insulation and the drywall. To what extent this matters, no idea. But it is barely bearable.
We actually have flawless values according to DIN, which specify the measurement in db(A), which in turn almost excludes low tones below 100Hz. However, these tones below 100Hz are extremely annoying and possibly even harmful to health (this has not really been "researched" yet, but it definitely does something to the body). Especially at 63Hz, it spikes up to partly 60db. It rumbles and drones in the bedroom and child's room. Especially in the child's room, I am very worried. So far, the BT has only partially relented and said that almost nothing can be done against these frequencies. He is not wrong, but it would be enough if an improvement of a few db could be achieved.
Maximum values can probably be read from the outdated DIN, but unfortunately, I do not have it at hand.