This sound comes from the theme associated with the 1975 film Jaws, with music composed by John Williams. The simple repeating motif became one of cinema's most recognizable danger cues and has been referenced for decades in comedy, TV, and internet edits. Online, people use short cuts of it to show an approaching person, animal, or problem before the moment fully arrives. It remains popular because the cue is instantly understood, even when the situation is harmless and played for laughs.