Horns

Basic Description

Car horns are simple electromagnetic devices that produce loud audible sounds to get the attention of nearby vehicle occupants or pedestrians. A typical horn is composed of a magnetic coil, an armature with a metal diaphragm, a pair of electrical contacts and a switch. When the driver activates the switch, the closed electric contact allows a current to flow through the coil. This generates a magnetic force that attracts the armature, as well as the metal diaphragm. This disconnects the electric contact and cuts off the current to release the armature and diaphragm. When they move back to their initial positions, the contact is closed again and the cycle repeats. This generates an oscillation of the diaphragm and creates the sound.

In general, there are two types of horn shapes: plate and spiral. The plate type has a small volume and light weight. It is also easy to be installed on a car. The other type usually adds a spiral duct to obtain a better sound effect. Most horns are used in pairs (low and high notes) to achieve a sound level of approximately 107-109 decibels.

Horns installed on trucks are usually purely acoustic devices driven by compressed air instead of current. Air horns can generate very loud sounds, typically at levels of 117-118 decibels.

Manufacturers

Hadley, Hella, Hornblasters, PIAA, Wolo

For More Information

[1] Horn (Acoustic), Wikipedia.

[2] How A Car Horn Works, www.secondchancegarage.com.