Horn (acoustic)

An acoustic horn or waveguide is a tapered sound guide designed to provide an acoustic impedance match between a sound source and free air. This has the effect of maximizing the efficiency with which sound waves from the particular source are transferred to the air. Conversely, a horn can be used at the receiving end to optimize the transfer of sound from the air to a receiver.

Acoustic horns are found in nature in the form of the burrows constructed by male mole crickets to amplify their song. The earliest appearance of the horn in connection to sound in The Times was published in 1786:

horn loudspeakers

and woodwind musical instruments

brass

such as those used on cars, trucks, trains, boats, and bicycles

vehicle horns

often used by lifeguards at public swimming pools.

megaphones

used to warn ships

foghorns

used by people who are hard of hearing (the human ear itself having the form of a horn)

ear horns

pickup horns, used e.g. on acoustic players