Advice - constant barking at neighbors

I need some advice for my 2 year old Aussie. He constantly barks at any noise he hears outside our apartment door. It could be as simple as a neighbor getting off the elevator. I know he’s just trying to protect his humans. Is there something I can do to help him understand he doesn’t have to bark? Like a white noise machine near the door? He gets plenty of exercise throughout the day so that’s not a problem for him. The barking mostly happens late at night due to neighbors working odd hours