Harbor Freight Air Horn

(Remember - safety first.)

It makes noise.

Lots of noise.

Specifically, it uses a 12VDC source, such as a standard car battery, to power an air compressor which sends air through a tube, which goes through a splitter to two tubes, which vibrates plates of some sort and directs disturbed air out the mouths of a pair of horns.

See?

It's advertised as 135dB, 10W. 10W/12V=0.85A. It comes with mounting hardware for installation in a car, but I'm not a car person, so I just hooked it up to a switch and an SLA.

It's loud. I measured its output as 120dB at 1m, which is supposedly as loud as a train horn at the same distance.

I made an improved version for a buddy when I saw this horn at rvtoyoutlet.com for $10 instead of the $15 I paid at HF. It has red horns, and a slightly different compressor, but it's basically the same thing. However, instead of a toggle switch, it has a NO pushbutton, and instead of its own battery, I attached it to a pair of meter-long 16AWG wires soldered to a cigarette lighter jack. All my buddy has to do is plug it in, sit the compressor on the dash or something, and push the button. I soldered all the wire/terminal connections, so it should be pretty decent.

Bottom line: BIG sound, for dirt cheap. You could connect one to a battery of 10 AA NiMHs if you wanted and carry it around, blasting it at will.

Again, safety first - activating something this loud can be dangerous without hearing protection.