LBS Has a Hornit on display , it seems seems loud, enough..

Best?, send me all of them and I can opine better as to ranking..
maybe send a VU meter, too, so I can gather Desibel data...

My Buddy brought his old Air Zounds on a Sail Boat trip from Orcas Isle to Olympia .
you need a horn to get the drawbridge across the canal to get to Lake Washington,
in Seattle, lifted, ... it was sufficient for that purpose..