The function of a car horn is to alert people to a potential danger related to a car. Listen to the various types of car horns.

A vehicle horn is a sound-making device used to warn others of the approach of the vehicle or of its presence. Automobiles, trucks, ships, and trains are all required by law in some countries to have horns. Bicycles in many areas are also legally required to have an audible warning device in many jurisdictions, but not universally, and not always a horn.