Writing a letter might sound like the polite way to approach the problem. However, if you write them a nice letter, and they are jerks, they may begin harassing YOU. And, if the police are ever called, they would automatically assume it was you that complained, and take vengeance. Remember, you have to live next to them. You want their attitude to be pleasant. I would call your county animal control (listed under county offices) and ask what the laws are, and how you can safely make a complaint...Our animal control just approaches homes and says they could hear the dogs barking from the next block, and came to see what the problem was......Perhaps yours does the same. Best of luck to you!