Train air horns have long been used on locomotives to warn at crossings, producing a powerful chord designed to carry over long distances. Online, short recordings of that blast were adopted by meme editors and soundboard users because the volume works even on small phone speakers. The very loud version circulates as a generic prank and reaction effect rather than a clip from a specific film or show, often added to near-miss jokes, fake collisions, and startled reaction videos where the joke depends entirely on sudden noise.