History and evolution of the foghorn
The foghorn is a sound device used to alert other vessels to the presence of a ship, particularly in conditions of fog or low visibility. Historically, the first maritime sound devices were bells, used as early as the Middle Ages. With the evolution of navigation techniques and the increase in maritime traffic, the need arose for a more powerful signal that could be heard over long distances.
The first mechanical foghorns appeared in the 19th century. They were powered by compressed air or steam. They quickly spread to large ships, especially steamships, and became an essential tool for maritime safety. Today, electric models, also known as boat horns, have replaced traditional mechanical devices, offering greater reliability and sound range.
The usefulness of the on-board foghorn
The main function of the foghorn is to signal the presence of a ship in conditions of low visibility. It helps prevent collisions at sea, particularly when a vessel is obscured by fog, rain or snow. The sound emitted by the foghorn is designed to be heard over long distances, even in difficult weather conditions.
Under the International Regulations for Preventing Collisions at Sea (RIPAM), the foghorn is required on board all vessels to communicate codified sound signals. These signals can indicate a maneuver in progress, a static position or an emergency situation.
The different types of foghorns: mechanical, gas and electric
There are several types of foghorns, adapted to the specific needs of each type of vessel:
- Wind foghorn this is the simplest and least expensive model, ideal for boaters. Simply blow into it to emit a powerful sound signal. Although inexpensive, it requires a certain lung capacity to be fully effective.
- Gas foghorn more powerful, it works with a gas cartridge. A simple press on the trigger releases the gas, producing an intense sound. Easy to use and hygienic, it's ideal for prolonged use. It is often mounted on the coachroof of motorboats or used on sailboats.
- Electric fog horns (horn) modern and easy-to-use, they replace mechanical models on many motorboats. They allow you to program different sound signals, while offering long autonomy.
Each type of foghorn has its own advantages. Boaters will prefer mechanical models for their portability, while professionals will often opt for more powerful electronic devices.
How the foghorn works
The principle of the foghorn is to amplify a sound produced by an air vibration or an electronic signal. For pneumatic models, a compressor or compressed-air cylinder feeds the horn, triggering the vibration of a membrane and producing the characteristic sound. Electronic horns, on the other hand, use a sound generator capable of emitting coded signals.
Sound frequency and intensity are standardized to guarantee their effectiveness. In general, a foghorn must be capable of emitting a sound of at least 120 decibels to be audible over a long distance.
RIPAM regulations and sound signals
The use of the foghorn is governed by the International Regulations for Preventing Collisions at Sea (RIPAM) . In conditions of fog or low visibility, navigation lights become insufficient. The foghorn then becomes the main tool for signalling the presence of a vessel and informing about maneuvers in progress. Here are the signals to be emitted according to the situation.
- Mechanically propelled vessel with headway it must emit a prolonged sound every two minutes maximum.
- Vessel with restricted manoeuvring capacity, sailing vessel, fishing vessel, or tugboat these vessels must emit three consecutive tones every two minutes, one long tone followed by two short tones.
These audible signals provide effective collision warning, even in zero visibility.
Sound signals when manoeuvring
The foghorn is also used to communicate specific manoeuvres:
- A short shot change course to starboard.
- Two short blows change course to port.
- Three short blows : reverse.
- Five shots or more signal of urgency or lack of understanding of another vessel's intentions.
Each signal has a precise meaning and must be mastered by boaters and professionals to avoid any risk of collision.
