Had a similar thing happen to me. I'd get the "stomp of dissaproval" from my upstairs neighbor all the time. One saturday morning when a car drove by in the parking lot with lots of bass - I got the stomp. I had to laugh... they were annoying as all get out - but never called the cops on me.

My revenge was more noise. I had a new amp - turned on my synth - made it go subsonic, so that you couldn't really hear anything, but you could 'feel' it.. [censored] would rattle. .. and I'd leave for the day. It was cool because you couldn't exactly tell where the sound was coming from.

If anything - it made me feel better.