[JoeyP]

Dogs hear many more things than we do
What you might think is nothing might be very easily heard by them
My two pups constantly get up and bark together at things I never hear

The other thing is that you said you scolded him
Don't do that
That might be why he's getting scared
My guys will often bark when they get frightened
and all it takes to make them stop is a pet and me telling them that it's ok
and they quiet down
other times if I go to the door with them and then say ... It's ok no ones there and walk away they will stop too