Foghorn

Foghorns are a Navigation aid for Mariners . In Fog gy conditions, when visual navigation aids such as Lighthouse s are obscured by the Weather , fog horns provide an Audible Warning of Rocks , Headlands , or other dangers to shipping. The first Automated Steam -powered fog horn was invented by Robert Foulis of Saint John , New Brunswick , Canada . The first model was installed on Partridge Island in 1859 , replacing the less effective Bell and Cannon which had been formerly used as warnings to ships in Fog .

The noise produced by a foghorn is very deep, due to the fact that deep sounds are audible to human ears at a greater distance than higher pitched ones. It is also very loud so ships a considerable distance away can heed its warning.

All foghorns use a vibrating column of air to create an audible tone, but the method of setting up this vibration differs. Many older foghorns, especially those on land, used Diaphone s to create the audible sound, producing a distinctive, deep and penetrating tone followed by an all-too-audible 'grunt', resulting in the famous two-tone sound that most people acquaint with foghons and the sea. Other horns used vibrating plates, similar to a modern electric car horn, or air forced through holes in a revolving cylinder, much in the same manner as a Siren (noisemaker) .

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Foghorn