Nuclear warning sirens descend from Cold War civil defence systems, where mechanical air raid sirens were installed in cities to warn residents of an incoming attack. Their distinctive rising and falling tone was designed to carry over long distances and be unmistakable against everyday noise. Recordings of those tests and drills later spread online as stock effects for films, games and disaster videos. This quieter version became popular on soundboards because it delivers the recognisable warning without the painful volume of many raw siren recordings.