Barking and Barking and Barking and BARKING...?

My two smallest dogs hit the door barking when I first let them out, because they know I won't let them continue - it's really quite funny, like they are trying to intimidate something that might be in the yard. But they know what "hush" means - it was just constant repetition and bringing them back in until they understood it wasn't acceptable. Other than that, I've heard one of those bark collars work! Good Luck!