Fog horns are devices that emit a deep tone to alert boaters of hazards during low visibility conditions. Modern foghorns emit laser beams to check visibility and are mounted on ships for collision avoidance. They are useful for small vessels and areas with rapidly changing coastlines.
A fog horn is a device that emits a prolonged deep tone during low visibility conditions to alert boaters to various hazards. Because the sound of a fog horn is so distinctive, many people associate fog horns with the sea, as they are often heard on visits to coastal regions. You may also hear the term “foghorn” used to describe someone with a piercing, resonant voice.
Various devices have been used for centuries along coastlines and on board ships to issue warnings during low visibility conditions. While headlamps can be excellent navigational aids, they are limited by visibility in your area, and during especially foggy or snowy conditions, boaters may not detect a headlamp’s light. As a result, many nations began firing cannons or ringing bells to warn mariners of things like shoals and rocks. By the 19th century, an early version of the automated foghorn had been developed, and today foghorn technology is quite advanced.
Modern foghorns emit laser beams periodically to check visibility. If the laser indicates visibility is low, a computer activates the foghorn and it will continue to sound until tests indicate conditions have cleared again. Foghorn notes are extremely low because low sounds carry better, providing more warning. For large ships that are difficult to maneuver, the more aware of navigational hazards the better.
You often see fog horns mounted on buoys and bridges, and they are also mounted on ships for collision avoidance. Although most ships have advanced navigation software that alerts them if they are approaching areas that are dangerous to navigate, ships have no way of knowing approaching ships without foghorns and other signals. Therefore, ships regularly test their fog horns to ensure they are in good working order.
For small vessels that lack sophisticated navigation systems, coastal fog horns can save lives when conditions turn nasty on the water. Foghorns are also very useful in areas with rapidly changing coastlines, as they act as a reminder to proceed with caution. By the way, many fog horns are two-tone because early fog horns used telephones, specially designed pipes that would produce a long tone followed by a growl when the air in the horn stopped resonating. Although the phones are no longer in use, people find them friendly and familiar, so the distinctive sound has been retained.
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