Wood privacy fence - planning over the top? Alternatives?

Apparently, this is all just pure theory? Coconut mats, old felt blankets, thujas. I would have tried some things on a meter long time ago... Enforce Sunday quiet and otherwise time slots for music or Kati's rest. That should be bearable. The neighbors seem to only need the music for gardening anyway. Hopefully. Next year the child will be at the point where it bothers the neighbors ;)

that his 2 meter tall, very old and dense thuja bushes basically do nothing?

Two meters tall is not sensible if it does not match the propagation characteristics of the respective sound - for a proper plan you would need measuring microphones at/in/with several positions / heights / angles; "dense" is wrong because then the sound has to deflect - where should it dissipate then? But it makes little sense if I, as someone with two-thirds knowledge, give a layperson a pro-seminar on the basics of acoustic construction, while there are professional experts for that in the Yellow Pages.

I am putting my suggestion from a few weeks ago back up for discussion: to drown out an unpleasant noise with a more pleasant one.

If you don't have a problem with the sound of running water, then a small stream along the affected border might be worth considering. Near the terrace, a powerful pump supplies a waterfall about one meter high, which creates a great sound. Additionally, there are two smaller drops (with stones that create swirling) further back in the watercourse. Perhaps also a strong water feature in a water basin halfway along. Normally running rather discreetly but equipped with a power button (or an automatic noise control): when the neighbor turns up the volume again, the pump goes to full power. Then only the mill by the rushing stream is clattering... you can also build all of this yourself, with stones, gravel, and pond liner.

I am putting my suggestion from a few weeks ago back up for discussion: to cover an unpleasant noise with a more pleasant one.

If you don’t have a problem with the sound of running water, then a stream at the affected boundary might be worth considering. Near the terrace, a strong pump supplies a waterfall about one meter high, which creates a great sound. In addition, there are two smaller cascades (with stones causing swirling) further back in the stream. Perhaps a strong water feature in a water basin halfway along as well. Normally running rather discreetly but equipped with a power button (or automatic sound control): when the neighbor turns up the volume again, the pump goes to full power. Then only the mill by the rushing stream clatters... you can build all this yourself with stones, gravel, and pond liner.

Do you have any example pictures or so of that?
In general, I find the sound of running water wonderful. We also have electricity available that we haven’t used yet. So it would definitely be worth considering. Can a stream/fountain or something similar cover such a noise?

Overpowering: yes. If the speaker is 8 meters away from you and the waterfall 2 meters, the waterfall will be perceived as 4 times louder at the same frequency and volume.

From the terrace, a boundary wall 400 cm deep, 200 cm high. It already absorbs some sound.

Now perpendicular to the wall, another wall 1.60 cm high (You can create a wind-protected seating area behind it) and from there 80 cm down with a waterfall:


From the remaining 80 cm height, it now goes down over several roaring rapids



After about another four meters, everything lands in a pond with a water fountain


and from there everything is pumped back up again.

Such a thing can be planned for you by a landscape gardener, depending on your skill you can also do it as a DIY project:
You can build the wall for the waterfall yourself from formwork blocks and facing bricks. A watercourse is available prefabricated in GRP, for the slope you still need some earth fill. And the pond basin itself is designed with pond liner. Add a powerful pump and a water spout. Done.

As a starter, there are also prefabricated basins like this—if your preferred lounge spot is directly next to it this could already be sufficient (but only for that!)

PS: Just take a boombox like the one your neighbor has with the most annoying song and sit by a rushing stream (I suppose that’s not so easy to find in northern Germany). Now see what distance you need from the stream or the boombox so that the music is no longer perceived as unpleasant. If this distance is realistically achievable for you, you must now try to recreate this soundscape as well as possible in your home.