This weekend I installed behind the grill a 100 watt (123db) Speaker Whelen electronic air horn. These are the same air horn your find on the fire trucks. The thing is LOUD!!! You can find info about the airhorn and pa at:
www.SafetyLeague.com
www.SafetyLeague.com
Whelen Airhorn & PA at SafetyLeague.com
Whelen Air Horn & PA
Whelen Speaker mounted inside HUMMER H2 grill
This set up is very concealed and far less costly than three chrome air horns. It is by far the best I've found for air horns.
Gary