Bi-level commuter trains are double-deck passenger trains used on busy suburban rail routes, and their horns are designed as warning signals for crossings, stations and track workers. The distinctive multi-chime blast is produced by air horns mounted on the locomotive or cab car, built to be heard over city noise at a distance. Recordings of these horns circulate among railfans and sound designers who document different lines and equipment. Online, the clip is reused wherever a believable modern passenger train sound is needed without filming a real departure.