[cbrand]

This is not "barking" this is sharp-shy behavior. This is very, very serious because it can escalate to biting if a dog feels threatened.

You need to contact a good behaviorist right away and get a professional opinion about how best to handle this behavior.

I might also have his eyes checked by a certified Opthamologist.

 

[cbrand]

So he feels more secure on a leash. Based on that, I think I would leash him up even in the house if you have guests.

Still, going on your description, I would say that this behavior is motivated by fear. I'm always very nervous about this because my neighbors had a Standard Poodle named Baxter who behaved in a similar way. Baxter eventually bit a 12 yr old boy who surprised the dog as he went to jog past him on a trail in Boulder (bit him rather badly actually).

Please contact a behaviorist.