Why don't you offer to pay to have your neighbor move it to the back yard and/or get a quote on a new quieter one but moving may be the better option. Tell him you are going to spend a few hundred bucks to fix the problem and it would be easier and better to move it and you would rather pitch in the money to do that. Besides if it is next to his bedroom window too, he may pitch in the most to do it. Neighbors should try to "get along", not get it on. Good luck and talk to your neighbor and post back with what he says. Next thing you know, he'll be inviting you over for dinner. Good luck.