What are legal car horn alternatives?

What are legal car horn alternatives?
Most U.S. States Vehicle Codes only specify that a vehicle horn may not exceed the standard 110 decibels, or otherwise emit a harsh, or unreasonably loud sound.You may NOT equip, or otherwise replace your vehicles horn, with any siren, whistle, bell, or other type of audible warning device that is intended for emergency vehicle use only, if in fact your vehicle is NOT an emergency vehicle. (If you're a volunteer firefighter, check with your department for usage regulations.)I know of people who have substituted their vehicle horn for a boat horn-- that is, one that produces the same volume, but at a much higher pitch than a standard passenger car horn. Provided you don't abuse or "overuse" the horn, I doubt anyone in law enforcement will pay too much attention to your having it.For your State's Vehicle Code, which would outline the specifics for your own State, run a search in Google. Example: "Pennsylvania Motor Vehicle Inspection Code". Or call your local State Police Agency with questions.