My dog used to do it to...barking at nothing in particular, especially at night. Why don't u try using the dog muzzle? It will hold him down for a while, BUT REMEMBER DON'T LEAVE HIM IN IT FOR A LONG TIME, take it off after a little while. My dog always simmer down whenever I show her the muzzle..it was like associating the muzzle to silence. For me it works. Hope that it works for u too. Good Luck!!! =)

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e.m.s.