My recommendations:
1. Talk to him again, but this time be wearing a stern expression. I've seen said stern expression- it should work.

2. White noise. You can get one that makes the sounds of waves, or rain, or crickets, or a number of others. It doesn't have to be loud to work. For that matter, you can get a CD of nature sounds and put it on repeat.

3. If neither of the above does it, then I suggest the speakers against the wall and the fake council letter. Say that he's been making the neighbors' pets try to chew on their own ears, and he will be responsible for any veterinary bills.

EDIT: Or play this video, REALLY LOUD. www.youtube.com/watch?v=W7u2Sy73B6Q
( The Resident Loon Not a demographic. Do not measure., Wed 12 Nov 2008, 12:56, Reply)