A Little Big Horn

As I was working on our review of sound signaling devices in our August 2016 issue, I took a look on the web for homemade foghorns. I found quite a number of websites and videos that showed how to make foghorns and train horns out of common plastic pipe and fittings. A trip to the hardware store for some 1/2″ PVC pipe and fittings, and 30 or 40 minutes of puttering in the shop was all it took to come up with a few configurations that made a sound that I liked.

The parts are common plastic pipe and fittings. Only the two reducers need modifying: The one at the back of the horn (left) is shortened and the one at the front reamed out to let the pipe slip through.

The core of the horn is a 1″ x 1″ x 1/2″ T fitting and two 1″ to 1/2″ reducers. One reducer gets shortened up with a hacksaw. (Don’t try using a bandsaw—cylinders like plastic pipe do dangerous things in one.) The cut then gets sanded flat. The other reducer needs to have the stop inside removed so that 1/2″ pipe will slip through. The short reducer is inserted into one end of the T with a piece of freezer bag. The other reducer goes into the other end of the T, and a piece of 1/2″ pipe slips through until it comes in contact with the freezer-bag membrane. You blow through the small hole in the side of the T and adjust the 1/2″ pipe to get a tone. You can change the mouthpiece angle with pipe and angled joints. The length of the pipe slipped through the reducer will determine the horn’s pitch. You can use a long pipe or a short length of pipe—about 6″ so you can still get a grip on it to adjust it—and, if you like, connect a funnel to the pipe. The sound I liked best came from a 24″ length of pipe. It had a deep, resonant, rattling tone.