An air horn has a small air compressor which generates a movement of air through the device at speed. When the user of the horn presses the button, the horn creates a noise.

The compression is done at up to 10 bars. The air horn kit consists of an air horn and a compressor. The compression is done at up to 10 bars. The air horn kit consists of an air horn and a compressor.

A horn blows air and makes a noise

An air horn is a pneumatic device made up of compressed air which is passed through a horn to produce a very loud sound for attention and signalling purposes.

There really is only one way to turn off the air horn in a truck. You need to disconnect the horn.