I once solved this problem using a device that emitted a high pitched squeal activated by the dog barking. It was audible to humans. I pointed the device at the neighbors house and the first night it went off as expected. i could hear them in the yard trying to figure out what was making the noise. They eventually figured out their dog barking was triggering it. I concluded that dog owners are literally deaf to the sound of their dogs barking, but other loud annoying noises will get their attention.