foghorn
device that uses sound to warn vehicles of navigational hazards like rocky coastlines, or boats of the presence of other vessels, in foggy conditions
en-US/ˈfɑɡˌhɑɹn/
en-GB/ˈfɒɡhɔːn/
device that uses sound to warn vehicles of navigational hazards like rocky coastlines, or boats of the presence of other vessels, in foggy conditions