An air horn typically has a canister or reservoir that stores compressed air, a valve mechanism to regulate the air release, and a horn or diaphragm to amplify the sound. When the valve is opened, the compressed air rushes through the horn or diaphragm, making an audible noise that attracts attention.
There are numerous sizes and types of air horns. Some air horns are portable and include a manual activation option, while others are built into vehicles or other machinery and have a button or lever that must be pulled to start. An air horn can be a useful communication tool in some circumstances since its loud, long-distance sound can be heard clearly.
Air horns can be useful in certain situations, but they should be used sensibly and considerately, taking into mind local noise ordinances and any potential effects on nearby residents.