Put a tri-tone air horn on my '09 Fit this weekend. Might be the best thing I've done to this car, quite enjoyable. I have been battling leaks, and still have a leak however, so it won't be really operational until I can nail that down.

Horrible video, to give you an idea of how it sounds (notice the sound echos off of buildings)
‪Train horn on my 2009 Honda fit‬‏ - YouTube

Supposed 140dba, but I have no idea what it really is. Using a paintball CO2 20oz canister loaded with 12ozs, an old regulator I got from a friend off a soda system pushing 120psi on the lowside, and a few adapters. Probably about $80 into it.

Setup:


Mounted in rear / on bumper / on trailer hitch.

 

That's awesome!

 

nice...so much better than the stock horn!