Anxious 2 1/2 year old. Protective, barks at random noises. Seems like he's always on guard.

Hi y'all. Brixton was doing better but has begun showing anxious behavior in the house again. I would not call it seperation anxietly but rather protective anxiety... he'll hear a noise outside (were in the city) like a passer by or other dog and it will set him off. Our doors are open in the summer and this behaviour has become more frequent.
We cant always identify what sets him off and as it sometimes is a random noise in the house aswell.
His reaction is essentially barking and pacing back and forth for a few minutes until he calms down.
We've recently tried the crate again while we are out during the day so he can appropriate his own safe space rather than feel the need to protect the whole house.
Great dog otherwise!!! With a baby on the way i'd appreciate any input anyone may have. I'm determined to find a solution and have a calm and quiet household for our new arrival