Loud horn?

Looking for a horn loud enough to give old ladies a heart attack, but, I am not comfortable messing with compressors and rewiring my fuse box so some sort of plug and play or minimal skills needed would be appreciated.

 

A few trucks ago, I put one of these on, connects the same as a replacement horn
and it was pretty freakin loud for a self contained horn.

http://www.amazon.com/Stebel-Nautil...1461690653&sr=8-1&keywords=motorcycle+airhorn

 

Any horn you add is going to need a dedicated circuit to the battery, activated via a solenoid off the existing horn wire. If you wire it as a replacement off your existing wiring, it's not going to be any louder than your existing horn, because those wires aren't heavy enough gauge to carry any more current than the existing horn draws.