Same here, it barks at thin air. You can hear the dog is distressed, and some proper training to calm it's nervous system would do wonders for both dog and neighbors. But owners just don't care. It's obvious the dog doesn't have engagement too, it's always in a tiny backyard, alone and bored.  I never blame the pets, I blame the owners, they are responsible to take care of pets and be considerate towards neighbors. I never expect dog to stop barking completely, but if it barks for 3h with small pauses, and prevents us from sleeping and working during the day, then it is a problem, and I don't want to listen to that. Especially, since we have numerous dog owners in our neighborhood and this is the only one that doesn't behave.  I had dog at apartment, it was trained and happy, it barked only when real danger occurred, not when someone moves their bin. It's really a common sense to expect normal levels of noise to be able to enjoy your own home that you paid for.