On a calm day, you can see for miles from your boat, and it may be difficult to imagine why you might need to signal with sounds – all boats are visible and seem easy to avoid. However, this is the ocean and all sorts of unexpected conditions may arise. The weather can change faster that you thought possible, or other boats may suddenly lose control. For all these possibilities, and for a generally safer boating experience, it is best for boaters to learn how to signal their intentions and positions with sound.

Below is a guide to sound signaling, along with the devices used to do it and the regulations attached to them.

Types of Sound-Producing Devices

Whistles are capable of acting as signals, although they are not as loud as air horns. Their particular advantage is that, due to their small size, they may easily be hooked to a lifejacket or belt loop. Many boating programs and regattas for children and teenagers in fact require that participants have a whistle on them at all times for just such purposes. The Coast Guard’s regulations on sound-producing devices mention whistles as the basic device.

Fog or air horns are a more modern device for creating sound signals, and are very commonly seen on all sorts of boats. They are loud and easy to use – just press the button on the top and you will get a blast that can be heard for seemingly miles around.

The ship’s bell is the oldest of the sound-producing devices, having been used on all sorts of vessels for hundreds of years. For most boaters, these are too ornate and bulky, as they must be mounted in order to be used. They do, however, give a certain elegance to vessels with the capability to affix them.

Regulations on Devices for Boats

The Coast Guard mandates that vessels over 12 meters (approximately 40 feet) be equipped with at least a whistle. Vessels over 20 meters (approximately 65 feet) must be equipped with at least a whistle and a bell, and vessels over 100 meters (approximately 328 feet) must be equipped with at least a whistle, a bell, and a gong. The devices used to produce sound do not need to be exactly those mentioned above; they just need to be capable of producing an equivalent sound to those devices mentioned in the regulations.

As far as the devices themselves are concerned, horns or other sound-producing devices must be audible for half a mile. Look for the Coast Guard stamp of approval on any air horn that you are planning to buy.

Common Sound Signals Used

Sound signals are comprised of short and long signals. Short blasts last approximately one second, long enough so that it can be heard but not too long that it is mistaken for a long blast. Long blasts should last about four to six seconds.

In general, sound signals are used under two conditions. The first is that a boater wishes to inform another boater of where they intend to go or any change in their location without attempting to hail them on the radio with its many channels. The second is that weather conditions have limited visibility to the point that sound becomes necessary to indicate both position and direction to other boaters in the area. 

Below are some common sound signals:

1 short blast indicates your intention to turn to starboard or to overtake another boat on your starboard side (their port side). 

2 short blasts indicate your intention to turn to port or to overtake another boat on your port side (their starboard side).

3 short blasts indicate your intention to operate under reverse propulsion, which in simpler terms is “back up.”

Sound Signals to Indicate Movement 

For signals that indicate a proposed movement or maneuver, the boat being signaled to will return the same signal if it understands and is in agreement. For example, if you give one short blast to a boat ahead of you, it will give one short blast in return to tell you that it understands and agrees that you are planning to pass on its port side.

5 short blasts are an immediate warning. A boat will give five short blasts if it feels that another boat is on a collision course or otherwise dangerously close, or if the signal of the other boat has not been understood or agreed to.

If you hear this signal, slow down at once and communicate further with the boat that gave it until a safe course for both boats has been established. Hearing this signal may also mean that you are in the danger area of an obstruction or other obstacle.

1 long blast is a less immediate warning that should be used when coming around a bend or other object that obstructs the view; it communicates your position to other boaters and warns them that you are coming.

Boating Signals in Poor Visibility

In addition to these, there are sound signals for specific use in conditions of low visibility. They are as follows:

Powerboats or sailboats under power must give signals of 1 long blast every 2 minutes to indicate their changing position as they move through the water.

A powerboat or sailboat under power that is stopped (not moving through the water) must give signals of 2 long blasts every two minutes to indicate their position.

A sailboat or any boat that is restricted in its ability to move, towing or pushing another boat, or is currently engaged in fishing, must give 1 long blast and 2 short blasts every two minutes.

If you are boating in conditions of restricted visibility and you hear any of these signals, slow down to minimum speed until you can safely ascertain your relative positions and move forward without a collision. 

Sound signals are not totally necessary during days of clear visibility, as long as you keep a safe distance between yourself and other boats, but they are a must on foggy days. As long as you learn the signals and are able to use them at the appropriate time, you won’t be taken unawares when conditions turn bad.