A horn is the voice of your car. It tells pedestrians and other vehicles to stop, move or speed up, or it may announce your arrival before a date. Though most car horns sound fairly similar to each other, there are different types of horns for speciality vehicles, such as police cars or for accessorising your own ride. The sound of your horn can be customised to your tastes just as much as the car itself.
Most modern automobiles use a horn that consists of a flexible metal diaphragm, an electromagnetic coil, a switch and housing to amplify sound. The device functions so that when you honk, an electrical current runs through the coil to make the diaphragm oscillate back and forth. The oscillations cause the air to move through the acoustical housing and produces a loud sound. It takes a lot of power to produce a noise that often exceeds 90 decibels, so the horn uses more electrical power than even the starter.
Electric horns are activated from your car battery and look like loudspeakers that can be mounted to the roof. Electric horns can be much louder than typical automobile horns. Police cars often use them to get the attention of a motorist. On the lighter side, electric horns can be used for customising your vehicle in clever ways. If you want a horn with a wolf whistle or a few notes from "Dixie" like the car in the TV show "The Dukes of Hazzard," get an electric horn. One vendor even sells a musical car horn that is preprogrammed with 34 different songs and a songbook with 148 additional songs. You also can play and record your own 28-note melody.
You may have seen air horns at amateur sporting events to announce the end of a quarter. They are aerosol-shaped cans with a horn-shaped top that emits a very loud noise when pressed down. Air horns work by compressing air in a small space. When the pressure gets released, it causes the horn to make a very loud noise. Ambulances, fire trucks and large vehicles often use air horns, though anyone can get one for his car. The horns can be wired for activation directly through the steering wheel.
Bulb horns were used in the early days of automobiles. You probably won't see them used except by clowns at a circus. The bulb horn contains a squeezable bulb that produces a sound through a metal reed. The horn was attached to the driver side of the automobile for easy access. They are mostly of ornamental value today since they cannot produce the loud noises of modern car horns.