Neighbor Pushed To The Edge, Threating Violence

[Donny Random]

I recently bought a duplex, I live in one side, three college aged men live in the other.

The neighbor next door, has complained about the noise they have been making. The various complains come every couple of months. One time my tenants were recording using amplified instruments, which was way too loud. I told them to stop, they stopped. Other times it has been various things like yelling outside late at night, blocked his drive way or tonight he said they slammed their side entrance door and woke him up. I talk to them when he makes a complaint about a particular situation and they know that the neighbor complains about the noise.

I am at a loss what to do. I want my neighbor to be happy. He is a nice older man with health problems that cause him constant pain. The tenants make loud noise so intermittently, every couple months based on my neighbors complains, that it does not seem like an a huge problem to me. But from my neighbors perspective (from my observations) it is like chinese water torture and he is just waiting for the next drop to come. And it has pushed him to the point where tonight he told me if they bother him again he will psychically harm them.

Can you offer advice to what my course of action should be?