{{Short description|Sound-making device for moving vehicles}} {{redirect|Car horn|the song|Car Horn (song)}} thumb|The single reed bulb horn was popular on early automobiles. {{Listen | filename =Car Horn.wav | title =Car horn | description =The sound of a typical car horn | pos =right }} 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” (older vehicles) or either a "beep" or a "honk" (modern vehicles). 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== {{More citations needed section |date=January 2011}}
===Motor vehicles=== [[File:RollsRoyceHorn.jpg|thumb|Horn of Rolls-Royce Phantom I Open Tourer Windovers (1926)]] thumb|Modern electric horns mounted in engine compartment
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, once spiral shaped, to better match the acoustical 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.
Horns can be used singly, but are often arranged in pairs to produce an interval consisting of two notes, sounded together; although this doubles the sound volume, the use of two differing frequencies is more perceptible to the human ear than two horns of the same frequency, particularly in an environment with a high ambient noise level. Typical frequencies of a pair of horns of this design are 500 Hz and 405–420 Hz (approximately B<sub>4</sub> and G{{music|sharp}}<sub>4</sub>, minor third) <ref>{{cite web |url=https://bikeresearch.net/articles/en/two-tone-car-horn-psychoacoustics/ |title=The Psychoacoustics of the Two-Tone Horn |last=Lansey |first=Jonathan |date=2025-12-08 |website=Bike Research |access-date=2025-12-08 |language=en}}</ref>.
Most cars, motorcycles, and motor scooters have for some time used a cheaper and smaller alternative design, which, despite retaining the name "horn," abandons the actual horn ducting and instead relies on a larger flat diaphragm to reach the required sound level. Sound levels of such horns are approximately 109–112 decibels, and they typically draw 2.5–5 amperes of current. Again, these horns can be either single, or arranged in pairs; typical frequencies for a pair are 420–440 Hz and 340–370 Hz (approximately G{{music|sharp}}<sub>4</sub>–A<sub>4</sub> and F<sub>4</sub>–F{{music|sharp}}<sub>4</sub>) for this design.
thumb|Diagram showing how a car horn works
A horn grille is a part of some designs of car or other motor vehicle that has an electric horn, such as a motor scooter.
Larger, louder air horns, as found on trucks (lorries) and buses, are driven by air compressors, or supplied by reservoirs charged to operate their air brakes. The compressor forces air past a diaphragm in the horn's throat, causing it to vibrate. Usually two are used, with varied frequencies generally lower than those of automobile horns, in the 125–180 Hz (approximately C<sub>3</sub>–G<sub>3</sub>) range. Sound levels are approximately 117–118 decibels.
===Trains, trolleycars and trams/streetcars=== thumb|The Leslie S5T, a locomotive air horn with five 'chimes' [[File:Station Transilien - Bois-le-Roi - Passage TER ou Intercités (BB 26000 + Corail) - (Bois-le-Roi, FR77) - 29-07-2025 1.webm|thumb|A train horning at Bois-le-Roi.]]
In order to be heard at the longer distances that trains require to warn of danger or stop, their locomotives have pneumatic train horns that are both louder and lower in frequency than motor vehicle horns. Operated by compressed air from the train's air brake system, their sound level is 146–175 dB. In the United States, train horns are required to have a minimum sound level of 96 dB and a maximum sound level of 110 dB at {{convert|100|ft|m|abbr=on}} in front of the train.
To distinguish their sound from truck and bus air horns, train horns in the U.S. consist of groups of two to five horns (called "chimes") which have different notes, sounded together to form a chord.
In Japan, most modern trains like 209 series or E233 series from the first half of the 1990s onwards use electric horns as primary in passenger use. Although electric horns were used by Seibu 2000 series, air horns were primarily used until the 1990s. Modern Japanese trains may still be equipped with both air horns and electric horns.
Most modern streetcars, trams and trolley cars including low-floor vehicles around the world also employ horns or whistles as a secondary auditory warning signal in addition to the gong/bell which either use the sound of air horns or electric automobile car horns.
===Ships=== [[Image:Supertanker Steam whistle, Merseyside Maritime Museum.jpg|thumb|Steam whistle from a supertanker, in Merseyside Maritime Museum, UK]]
Ships signal to each other and to the shore with air horns, sometimes called whistles, that are driven with compressed air or steam tapped from the power plant. Low frequencies are used, because they travel further than high frequencies; horns from ships have been heard as far as {{convert|10|mi|km|round=5|order=flip|spell=on}}.<ref>{{cite web |url=http://www.sterling.rmplc.co.uk/visions/funnel2.jpg |title=The "Voice" of the "Queen Mary" can be heard ten miles away! |access-date=2011-11-28 |archive-date=2023-01-10 |archive-url=https://web.archive.org/web/20230110214012/http://www.sterling.rmplc.co.uk/visions/funnel2.jpg |url-status=live }}</ref> Traditionally, the lower the frequency, the larger the ship. The RMS ''Queen Mary'', an ocean liner launched in 1934, had three horns based on 55 Hz (corresponding to A1 ), a frequency chosen because it was low enough that the very loud sound of it would not be painful to the passengers.<ref>{{cite web |url=http://www.sterling.rmplc.co.uk/visions/funnels.html |title=The Funnels and Whistles |publisher=Sterling.rmplc.co.uk |access-date=2011-11-28 |archive-date=2022-05-29 |archive-url=https://web.archive.org/web/20220529023424/https://www.sterling.rmplc.co.uk/visions/funnels.html |url-status=live }}</ref> Modern International Maritime Organization regulations specify that ships' horn frequencies be in the range 70–200 Hz (corresponding to C{{music|sharp}}<sub>2</sub>-G<sub>3</sub>) for vessels that are over {{convert|200|m|abbr=on}} in length. For vessels between {{convert|200|and|75|m|round=10|abbr=on}} the range is 130–350 Hz and for vessels under {{convert|75|m|round=10|abbr=on}} it is 70–700 Hz.<ref>{{Cite Wikisource|title=International_Regulations_for_Preventing_Collisions_at_Sea|anchor=ANNEX_III_:_Technical_details_of_sound_signal_appliances|at=Rule 1(b)}}</ref>
Smaller craft typically use electric diaphragm horns.
Portable air horns driven by canned compressed air are also used, as well as for officiating sports events and recreational activities.
== Klaxon ==<!-- Other articles redirect here. --> {{redirect|Klaxon}} {{redirect|Awooga|the Calvin Harris song|18 Months#Promotional singles}} thumb|right|Sign on a rural road in the United States advising drivers to "SOUND KLAXON" (1920) {{Listen |filename=WWII submarine dive klaxon.ogg |title=Klaxon alarm |description=A sample of a submarine dive alarm used by United States Navy submarines during World War II |format=Ogg}}
A '''klaxon''' is a type of an electromechanical horn or alerting device. Mainly used on cars, trains and ships, it produces an easily identifiable sound, often transcribed onomatopoeically in English as "awooga". Like most mechanical horns, it has largely been replaced by solid-state electronic alarms, though the memorable tone has persisted. ''Klaxon'' was originally a brand name.<ref> Matthew F. Jordan, ''Danger Sound Klaxon! The Horn That Changed History'' (University of Virginia Press, 2023) [http://www.h-net.org/reviews/showrev.php?id=60170 online review of this book]</ref>
The klaxon horn's characteristic sound is produced by a spring-steel diaphragm with a rivet in the center that is repeatedly struck by the teeth of a rotating cogwheel. The diaphragm is attached to a horn that acts as an acoustic transformer and controls the direction of the sound.<ref>{{cite web |title=What kind of device is a Klaxon? |url= http://www.innovateus.net/innopedia/what-kind-device-klaxon |url-status=dead |access-date=1 June 2012 |archive-url= https://web.archive.org/web/20130207111151/http://www.innovateus.net/innopedia/what-kind-device-klaxon |archive-date=7 February 2013 }}</ref>
In the first klaxons, the wheel was driven either by hand or by an electric motor. American inventor Miller Reese Hutchison (later chief engineer of Thomas Edison) patented the mechanism in 1908.<ref>{{US patent |923048 |Mechanically-actuated Acoustic Apparatus and Method}} US Patent 923,048. Applied March 14, 1908, granted May 25, 1909.<br /> {{US patent |923049 |Cam-operated Horn}} US Patent 923,049. Applied May 16, 1907, granted May 25, 1909.<br /> {{US patent |923122 |Mechanically-actuated Horn or Alarm}} US Patent 923,122. Applied May 16, 1907, granted May 25, 1909.</ref> The Lovell-McConnell Manufacturing Company of Newark, New Jersey bought the rights to the device and it became standard equipment on General Motors cars.<ref>{{cite news |title=The Klaxon Warning Signal |date=April 8, 1908 |pages=411–412 |work=The Horseless age: the automobile trade magazine |volume=21 |number=15 |url=https://books.google.com/books?id=xClhG6eV7gAC&pg=PA411 |access-date=January 16, 2011}}</ref> Franklyn Hallett Lovell Jr., the founder, coined the name ''klaxon'' from the Ancient Greek verb ''klazō'', "I shriek".<ref>{{cite news |title=Signalling Methods Definitely Cared for |volume=22 |date=January 13, 1910 |work=Automotive Industries magazine |publisher=Chilton company |location=New York |pages=125–126 |url=https://books.google.com/books?id=TdQqAAAAMAAJ&pg=PA125 |access-date=January 20, 2011}}</ref>
Klaxons were first fitted to automobiles and bicycles in 1908. They were originally powered by six-volt dry cells, and from 1911 by rechargeable batteries. Later hand-powered versions were used as military evacuation alarms and factory sirens. They were also used as submarine dive and surface alarms beginning in the Second World War.
===In other languages=== Several languages have either borrowed or transcribed the name into their lexicons. In Japanese, the word {{Nihongo|"klaxon"|クラクション|kurakushon}} refers to car horns in general. This is also true in languages such as French ({{lang|fr|klaxon}}), Italian ({{lang|it|clacson}}), Greek ({{lang|el|κλάξον}}), Dutch ({{lang|nl|claxon}}), Russian ({{lang|ru|клаксон}}), Polish ({{lang|pl|klakson}}), Spanish ({{lang|es|claxon}}), Romanian ({{lang|ro|claxon}}), Bulgarian ({{lang|bg|клаксон}}), Czech ({{lang|cs|klakson}}), Turkish ({{lang|tr|klakson}}), Indonesian ({{lang|id|klakson}}), some Arabic dialects ({{lang|id|كلاكسون}}) and Korean ({{lang|ko|클랙슨}}).
==Regulation== [[File:No Trumpeting Allowed (5375683446).jpg|thumb|Automobile horn use may be prohibited in certain areas, as indicated by this sign in Jalalabad, Afghanistan.]] [[File:Sound Horn sign on truck south of Chennai.jpg|thumb|350px|''Sound horn'' to overtake sign on truck south of Chennai, India]]
In countries applying the Vienna Convention on Road Traffic, usage of audible warnings is limited, and allowed only in two cases:<ref>See Vienna Convention on Road Traffic</ref> * to avoid an accident; * outside built-up areas to warn a driver that they are about to be overtaken.
==As musical instrument== {{Further|hornophone|klaxophone}} thumb|Taxi horns for Gershwin's ''An American in Paris'' Various types of vehicle horns are used by percussionists as sound effects, or even melodically, in musical works.<ref name="grove">{{Cite Grove|title=Sound effects |first=Hugh |last=Davies |id=47631}}</ref> For example, George Gershwin's 1928 orchestral work ''An American in Paris'' calls for the use of 4 taxi horns.<ref>{{cite web |title=60th Season 2012 - Program Notes |first=Richard E. |last=Rodda |date=11 August 2012 |publisher=The Peninsula Music Festival |publication-place=Ephraim, WI |url= http://www.musicfestival.com/new/reference/programnotes/prognotes2012/2012prog3.php |access-date=5 December 2012 |archive-url= https://web.archive.org/web/20120822001520/http://www.musicfestival.com/new/reference/programnotes/prognotes2012/2012prog3.php |archive-date=22 August 2012 |url-status=dead |df=dmy-all }}</ref> György Ligeti's opera ''Le Grand Macabre'' features two "Car Horn Preludes" scored for 12 bulb horns, each one tuned to a specific pitch.<ref>{{cite web |title=Toot Your Horn! |work=WQXR Blog |publisher=WNYC Radio |publication-place=New York |date=3 June 2010 |first=Naomi |last=Lewin |url=https://www.wqxr.org/#!/blogs/wqxr-blog/2010/jun/03/toot-your-horn/ |archive-url=https://web.archive.org/web/20151231210417/https://www.wqxr.org/#!/blogs/wqxr-blog/2010/jun/03/toot-your-horn/ |archive-date=31 December 2015 |url-status=dead |access-date=24 July 2024 }}</ref>
The hornophone consists of a set of bulb horns tuned to a chromatic scale and arranged as a musical keyboard on a frame like a xylophone. The klaxophone is a similar musical instrument using a set of klaxons.
===Other uses in music=== The song ''Car Alarm'' by Too Many Zooz is based on the sound of a honking horn.<ref>{{Cite web|url=https://www.phillyvoice.com/band-too-many-zooz-base-entire-new-song-philly-car-alarm-music-video/|title=This band managed to base an entire song off a Philly car alarm|website=www.phillyvoice.com|date=27 September 2018|access-date=2019-05-07}}</ref> The song ''Runnin’ With The Devil'' by Van Halen opens with a recording of car horns that swells to a crescendo and then is slowed down to drop the pitch.<ref>{{Cite web|url=https://www.vhnd.com/van-halen-i/runnin-with-the-devil/|title=Runnin’ With The Devil|website=www.vhnd.com|date=2013|access-date=2025-06-20}}</ref>
==See also== *Bicycle bell *Civil defense siren *List of auto parts *Vehicle-mounted siren *Vehicle-mounted whistle
==References== {{reflist}}
==External links== {{Wiktionary|klaxon}}
*[http://www.policeinterceptor.com/navysounds.htm Authentic Navy Alarm Sounds] *[http://www.delcoremyhistory.com/Service%20Manuals/klaxon%20horn%201933.htm Pages from a klaxon horn adjustment manual] with diagrams
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