My sympathies. I guess as others have said the Gemeinde is your best bet at sorting this out in a Swiss-acceptable way.
The guy's response about the 80 decibels is just so annoyingly

but I suppose to be expected from one who would cause such a situation in the first place.
I would be tempted to buy a decibel meter, the below CD, and play it in the back yard at precisely 80 decibels, on repeat, again and again until the dunce gets the message. Good luck.