Vehicle horn
sound-making device equipped on vehicles
A horn is a sound-making device installed on motor vehicles, trains, boats, and other types of vehicles. The sound it makes usually resembles a "honk" or a "beep". The driver uses the horn to warn others of the vehicle's presence or approach, or to call others' attention to a hazard. Motor vehicles, ships and trains are required by law in some countries to have horns. Public transit vehicles and even bicycles are also legally required to have an audible warning device in many areas.
Types
Motor vehicles
Modern car horns are usually electric, driven by a flat circular steel diaphragm that has an electromagnet acting on it in one direction and a spring pulling in the opposite direction. The diaphragm is attached to contact points that repeatedly interrupt the current to that electromagnet causing the diaphragm to spring back the other way, which completes the circuit again. This arrangement opens and closes the circuit hundreds of times per second, which creates a loud noise like a buzzer or electric bell, which sound enters a horn to be amplified.
A traditional style automobile horn includes an expansion chamber cast into its body (formerly spiral shaped) to better match the impedance of the diaphragm with open air and thus more effectively transfer the sound energy. Sound levels of typical car horns are approximately 107–109 decibels, and they typically draw 5–6 amperes of current.
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This entry incorporates text from “Vehicle horn” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.