A foghorn is a device that produces a loud, deep sound to warn vehicles, especially boats and ships, of navigational hazards such as rocky coastlines or other vessels during foggy or low-visibility conditions. It is primarily used in marine transport to provide an audible warning when visual aids like lighthouses are obscured by fog. The sound is designed to carry over long distances and is typically low-pitched because low-frequency sounds travel farther and are less affected by atmospheric interference in foggy weather. The first automated steam-powered foghorn was invented by Robert Foulis in Canada in 1859. Foghorns operate by creating a vibrating column of air to generate sound, using mechanisms such as vibrating plates, rotating cylinders, or air compressors. Over time, foghorn technology has evolved from steam- powered to more modern electric versions. Foghorns are an iconic and crucial safety tool in maritime navigation, helping sailors avoid dangerous obstacles during poor visibility conditions. They are also sometimes used figuratively to describe someone with a very loud voice.