Navigation Sound Signals: Reference for Recreational Boaters
Sound signals play a key role in boat navigation. In fact, they are one of the approved types of navigation aid used throughout the United States.
Sound signals are effective even in poor visibility and at a distance. However, their use is restricted to specific situations, and boaters must know how to correctly use and interpret sound signals in order to boat safely and legally on U.S. waters.
Sound signal equipment requirements
Boaters in the U.S. are legally required to carry sound signal equipment on board. The type of sound-producing equipment you must carry on your boat depends on its length:
- Boats under 39.4 feet: Must have at least one efficient sound-producing device. This can include a bell, whistle, or air horn. While items like guns, or pots and pans, can make noise in an emergency, it’s best to carry designated signaling equipment.
- Boats between 39.4 feet and 65.6 feet: Must have both a whistle and a bell.
- The whistle must be audible for at least half a nautical mile.
- The bell must have a mouth opening of at least 7.87 inches in diameter.
When to use sound signals
There are two main types of sound signals used in boating. One set of signals is used in situations of poor visibility, such as fog, mist, smoke, heavy rain or in darkness. Another set is used when vessels can see each other, but need to communicate important navigational or safety information.
Let’s look at each type in more detail.
Sound signals used in restricted visibility
Boat sound signals used in restricted visibility are specific patterns of blasts that vessels use to alert other boaters of their presence and actions. These signals are crucial for safe navigation when visibility is limited. Here are the main sound signals used in restricted visibility:
Vessel and situation |
Sound signal |
| Power-driven vessels underway | One prolonged blast every two minutes |
| Sailing vessels underway | One prolonged blast followed by two short blasts every two minutes |
| Power-driven vessels underway but not moving | Two prolonged blasts every two minutes |
| Vessels at anchor | Five seconds of rapid bell ringing every minute |
| Vessels run aground | Three bell strokes, followed by five seconds of rapid bell ringing, then three more bell strokes, repeated every minute |
It’s important to note that when operating in restricted visibility, boaters should reduce their speed to the minimum needed to maintain course and be prepared to maneuver if there’s a risk of collision. To learn more about fog signals, refer to the Code of Federal Regulations, Inland Rules, Rule 35.
Maneuvering signals
In good visibility conditions, boats use specific sound signals for navigation to communicate their intentions to other vessels. These signals are used when vessels are in sight of each other and are on course to meet or cross at a distance within half a mile.
They help prevent collisions by clearly communicating which way a vessel is planning to go before they begin to move in that direction.
To use sound signals correctly, you must have a full grasp of the difference between port and starboard.
The main sound signals used for navigation in good visibility are:
Sound Signal |
Maneuver |
Response |
| One short blast | “I intend to leave you on my port side” or “I am altering my course to starboard (right)”. | The other vessel must acknowledge and agree to your intended action with one short blast. They are responsible for maintaining their course and speed to minimize the risk of collision. |
| Two short blasts | “I intend to leave you on my starboard side” or “I am altering my course to port (left)”. | The other vessel must acknowledge and agree to your intended action with two short blasts. They are responsible for maintaining their course and speed to minimize the risk of collision. |
| Three short blasts | “I am operating my boat in reverse” or “My engines are going astern”. This is usually preceded by one long blast to indicate you are getting underway. | No response required |
| Five short blasts | “Danger” or “I am unsure of your intentions” or “I do not understand your intentions”. This can be used if you do not understand the sound signal from another boat, or if you think that their intended maneuver is dangerous. | No sound signal is necessary, but the boat must respond to the communication with appropriate action. |
| One prolonged blast | Used as a warning signal, typically when coming around a blind bend or leaving a dock (for motorized boats 12 meters or longer). | Other vessels must respond with one prolonged blast.
This alerts the initiating vessel to the presence of other boats around the bend. It also helps both vessels pinpoint each other’s location. |
A short blast lasts about one second, while a prolonged blast lasts between four to six seconds.
Note: The above information represents Inland Rules regarding sound signals. These may differ from International Rules. Boaters are responsible for learning the difference if they intend to travel outside of the United States.
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