A HongKong made flashlight siren purchased on eBay just arrived.
I am truly surprised that most of it's sound comes from it's rotor intake compared to holding it with my ear beside the stator openings.
I'll have to try such a comparison with our Q siren.
So, perhaps the flared bell on the front of many old siren intakes DOES
help couple sound to the air and "amplify" it forward!
I thought it was just for looks or to help air morefficiently enter the rotor.