I’ve been told that all you need is a recording of the pump-action shotgun - the most recognized sound of “i mean business”
When I was in Iraq, I sometimes carried a Mossberg with all of the accessories (folding stock, heat shield, etc...), group of Iraqi policemen wanted to know what it was since it did not look any gun they had seen before. Since we were in the green zone, I decided to let them look at it, so I started shucking rounds to empty it. As soon as the policemen heard the distinctive sound of racking of a pump shotgun, they all started smiling and laughing. From what one policeman said, they had never seen in real live pump shotgun, but they had all watched American movies and that sound was the international sound of "Your in a heap of trouble."