Vehicle horn

Trams, trollies, streetcars, and even bicycles are also legally required to have an audible warning device in many areas.

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.

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.

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.

[2] Modern International Maritime Organization regulations specify that ships' horn frequencies be in the range 70–200 Hz (corresponding to C♯2-G3) for vessels that are over 200 m (660 ft) in length.

Mainly used on cars, trains and ships, it produces an easily identifiable sound, often transcribed onomatopoeically in English as "awooga".

[4] 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.

American inventor Miller Reese Hutchison (later chief engineer of Thomas Edison) patented the mechanism in 1908.

[6] The Lovell-McConnell Manufacturing Company of Newark, New Jersey bought the rights to the device and it became standard equipment on General Motors cars.

[7] Franklyn Hallett Lovell Jr., the founder, coined the name klaxon from the Ancient Greek verb klazō, "I shriek".

In countries applying the Vienna Convention on Road Traffic, usage of audible warnings is limited, and allowed only in two cases:[9] Various types of vehicle horns are used by percussionists as sound effects, or even melodically, in musical works.

[12] 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.