Ship horns have long been used as audible signals between vessels, with repeated blasts carrying specific meanings for maneuvering and warning in fog or busy waterways. A double blast is a familiar pattern heard in ports and harbors around large passenger and cargo ships. Online, recordings of these horns have been reused as standalone sound effects because the tone is instantly recognizable and carries well even on phone speakers. Editors keep returning to the two-blast version for its clean rhythm, which works as both a realistic harbor cue and an exaggerated announcement in short clips.