Vehicle horn Several languages have either borrowed or transcribed the name into their lexicons. In Japanese, the word refers to car horns in general, and in verb form () refers to sounding the horn. This is also true in languages such as French (), Italian (), Dutch (), Russian (), Polish (), Spanish (), Romanian (), Czech (), Turkish (), Indonesian (), and Korean (). In countries applying the Vienna Convention on Road Traffic, usage of audible warnings is limited, and allowed only in two cases: Vehicle horn A horn is a sound-making device that can be equipped to motor vehicles, buses,
Air horn or plastic horn or trumpet (called the "bell") attached to a small air chamber containing a metal reed or diaphragm in the throat of the horn. Compressed air flows from an inlet line through a narrow opening past the reed or diaphragm, causing it to vibrate, which creates sound waves. The flaring horn serves as an acoustic "transformer" to improve the transfer of sound energy from the diaphragm to the open air, making the sound louder. In most horns it also determines the pitch of the sound. When vibrated by the diaphragm, the column of air in the horn vibrates