Man, that really bites.* I feel for ya, for sure.* Nothing like a bunch of hicks living outside a hick neighbourhood, is there?
Do you have any way to measure how many decibels are actually being heard at the property line?* I mean, if they're under the ninety you mention, then you've got a problem if you don't like it.* 90 is pretty loud.* Stand about four feet away from someone running a chainsaw full throttle... that's ninety.
I personally don't know how a court will be able to enforce this.* You might be better off talking to the guy again before firing off that letter.* You don't want a neighbour war on your hands.* If the kids are stomping sprinkler heads, your 3 may be up for a keying one night, which would obviously not be worth it.
I'd bring a case of cold beer over when the guys doing yard work or something and have a friendly talk with him.* If he really likes you, then it will be harder for him to want to continue pissing you off.* If you bring him beer and he thinks you're a good guy you will have a better chance of getting compliance in a friendly manner.* I just think that threatening legal action is gonna be something you might regret; especially if he or his kids are complete assholes and they hate your guts.
food for thought.* Might not taste good though.
Anyway, I wish ya luck with whatever route you go. If you figure "fuck him" and want to go hardball... see if you can hire and bang his escort wife.