What's the protocol here?

I HATE our neighbors dogs. Since the day they moved in their two little dogs bark almost constantly. They live outside 24/7 and they bark at every little thing. Every time someone walks in front of their house, they bark. Every time a car drives down the ally, they bark. Every time we open our garage door, they bark. They bark from 3 to 3:30 pm every afternoon because the middle school is a couple of blocks away and kids walk by on their way home. There is an open field behind our house and when kids play back there the dogs bark constantly.

When they first moved in this past summer Mike was ready to call the cops the first day. I talked him out of it, saying that the dogs were probably just scared because it was a new place and that they would calm down when they got used to it. But they never stopped. They still bark constantly. We've gone over the house to knock on the door but no one ever seems to be home. We've called the police but I'm sure some annoying dogs are not high on their priority list.

I would never dream of disciplining someone else's child at the playground, what's the protocol with other people's dogs? When I was trying to put Olivia down for her nap earlier the dogs were barking like crazy so I stuck my head out the window and told them to hush. These dogs are in their own yard so I can see how it could be a total invasion of privacy for me to yell at someone else's dog but these dogs are obnoxious! Any advice?