ABSTRACT
Musicians play one type that traces back to blowing through a hollowed-out ram’s horn or conch shell. Automobiles are equipped with a third type of horn, which is intended to warn those in proximity. Similarly, some might consider a warning beeper to be the electronic equivalent of a horn, and a siren to be a horn that produces a continuous sound. Sirens take horns and beepers to the logical extreme. The attention-getting noise doesn’t stop and can typically change in frequency. Applications include ambulances, fire trucks, and severe weather alert systems. In the US, backup horns have typically been installed on heavy equipment, such as front-end loaders and forklifts. Their repeating sound might seem monotonous and habituating, but they are difficult to ignore and are intended to create a safer environment. One might consider them the offspring of whistles that alert people when a train is approaching.
