...>> “But the sound of a pump shotgun’ being racked has an even better effect.” <<
If you can endure the smell of fresh excrement...
When my wife and I traveled before carry permits were common,we always traveled with an 870 in the trunk.
I took it out and had it next to the nightstand in the second story motel room with a full tube and an empty chamber.
At 3:00 in the morning, someone kicked the door open by the second chain latch stopped it.
I grabbed the shotgun and racked it with the familiar,instantly recognizable clack, clack sounding loudly.
A female voice yelled,” Don’t shoot. Don’t shoot. We be leavin. We be leavin.”
And did they ever. Running down the stairs was a woman and her two felonious friends.
My nephew is a policeman and he told me they try to do the same thing if possible with a shotgun when they first confront a problem.
.
Actually I have a Remington .22 pump that has the same effect, but it poses less danger to the furniture.