Dog Barking Letter

What should I do about a neighbors barking dogs?
They bark all night. We went Tho neighbor's home and asked to silence. half the time she wont answer her door the other half, she said she was not his dogs bark. We wrote him a letter and referred it to shreds. We called the office prosecuters and they will send him a letter. To anyone who has experienced a Elese similar situation? What have you done? What happened? Advice?
A friend of mine has a neighbor who dog barks. She and her husband, after some "Beautiful", but failed discussions with the neighbor gave and bought an air horn. A quick silence noisy dogs on the Otherside of the fence. Relatively cheap and quick and efficient, at least in his situation.
Neighbor Dog Barks All Day