I've tried blasting music, loud sound effects, and other methods that didn't work very well. So, the other day I went to a hardware store and bought a large, hard, heavy rubber mallet, with a head that is 32 ounces. They were at it again on Friday, and a few strong strikes against the wall near, but not against, the ceiling, worked wonders. It must sound to them like the walls are going to come down. They've been a lot quiter since I did that - and if they complain to the landlard I'll just say that I'm hanging pictures or something. Anyway, it's a lot better and I hope I don't have to use the "weapon" again, but I will if they persist.