Joe, Joe, Joe,
In most jurisdictions, you don't get to fire a "warning" shot, especially at random outside your window, without some serious legal implications.
That said...I own a pump shotgun...and they won't hear it racking. They'll hear "BOOM" and then will probably be deaf and not hear the second round being chambered.
One in the pipe...always ready. No need to waste time loading the first round.