A horn is a sound-making device that can be equipped to motor vehicles, buses, bicycles, trains, trams and other types of vehicles. The sound made usually resembles a honk or a beep. Motor vehicles, ships and trains are required by law in some countries to have horns. Like trams, trolley cars and streetcars, bicycles are also legally required to have an audible warning device in many areas, but not universally, and not always a horn.
