Lighthouse foghorns have guided ships through fog since the nineteenth century, when steam-powered horns replaced bells and guns as a louder, more reliable warning for vessels near rocks and harbour entrances. Their deep tone was chosen because low frequencies travel farther through mist and over water than higher sounds. Today the sound is instantly recognised from films, documentaries and travel videos, where it signals the sea, isolation or approaching danger, and creators reuse short foghorn clips to give ordinary footage a coastal, cinematic atmosphere.