The foghorn is a long-standing real-world warning sound used by ships and coastal stations to signal their presence in low visibility. Online, short foghorn clips became popular as reaction audio because the deep blast instantly suggests danger, scale or exaggerated seriousness. It shows up in meme compilations, gaming edits and parody trailers, often filling the role of an over-the-top warning cue similar to a danger alarm sound effect meme. Its staying power comes from how quickly listeners recognize the sound and the mood it creates.