Perhaps our reaction should also be adapted to the particular sound of barking. for ex.: One of my Pits has to be on a chain for a while, (a chain long enough to reach her bed and water). Then, when I went away she used to whine and I used to run and look what's wrong and she was immediately quiet. But as soon I was out of sight she started again, very consistently. I'm sure with my behavior I reinforced her. Once I became aware of this, I endured her endless whining and in between she stops it after a few sounds.

Both Pits can bark awfully when something/someone approaches our yard. But then it is a real barking, very exited. When I hear this, I go in order to be sure what's going on. I'm trying do it in a way like to tell them: It's fine you alerted, but now it's my job to supervise, I say "quiet", (which they know from sessions), If they obey I praise and caress them and this works. (Unless I've not been aware of something, e.g once a snake between the waterhoses).

The level, Bob ones described, I haven't reached. He just needs to knock on a window, and the dogs shut up.

Don't know if my input makes sense for you all. Just wanted to say that listening to the many different kinds of barking are of importance to decide how we react.

Good to hear!