So the other day I realized something. The horn on my Focus sucks!!! It's not loud at all, and sounds like something the barbie mobile would have. How would you go about replacing it with a better horn? Do 18-wheeler horns work the same way?
My Svt has a double horn while your car probably only has a single horn. By simple logic, that making mine twice as loud as yours. This is one route you can go plus it never hurts to find a Crown Vic or some other large car in a salvage yard and swipe one of their horns.
From what I know, if you want a horn like an 18 wheeler, you have to add some form of air compressor unit in the car to supply the air to the air horns. It a fairly common so you shouldn't have any trouble finding information on it.
look around online for air horns. there are a lot of options for ones that are just a small compressor routed directly to the horns. much less complex than doing a truck or train horn which requires a compressor and tank (and may be illegal). I put one from oreilly's in my car a while back and it did make a big difference. only problem was I was with a pretty inexpensive one and the compressor died on me only a few months down the road. now it just takes up space in my car til I can either fix it or remove it.
After watching the movie Casino I did a 4-note "Cadillac" horn, sounds like a train without having some obnoxious, or possibly illegal horn set up. Plus I always wanted to do this to my Mustang but I never got around to it, and the Focus horn does suck.
I've got a crown victoria horn I pulled out of a junk yard police addition. They are super easy to get to, and certain years and plug and play, and you can bolt it in the factory location. Way better tone, much louder, <$5, and 10 minutes of work.