A device for sounding an alarm. On some entry level vehicles, a single horn makes a high pitch beep. On more expensive vehicles, the sound is made with two or more horns. The sound is made by an electrical charge which activates and deactivates a coil . The sound is then magnified by the shape of the horn. Large truck horns make a very loud noise because the sound is made by passing compressed air through the sounding device. A claxton horn makes a sound that resembles the word "A-hoo-gah." Also see air cleaner horn or air horn .