Sound Signals

Sound signals provide an audible means of conveying your intentions while operating in restricted visibility. Let’s take a look at what you need to know.

What exactly is “restricted visibility”?

Restricted visibility describes a situation where an operator can’t see hazards in their path or prevents their boat from being seen by others. Common examples include operating at night, during inclement weather (fog, for example) or when transiting an area where physical characteristics (like a sharp bend in a narrow river) prevent visibility.

Sound-producing devices

Sound signals are described as “blasts,” of which there are two types: A “short blast” is about 1 second in duration, while a “prolonged blast” is 4 to 6 seconds.

The word “whistle” is defined as any sound signaling device capable of producing the required blasts as described by Annex III of the USCG’s “Navigation Rules and Regulations Handbook.” While Annex III provides the technical characteristics of a proper blast (such as frequencies and intensity), a simple interpretation is how far the blast can be heard.

For example, the minimum range for a whistle or horn (both can be used interchangeably) required for a vessel 20 meters (65.6 feet) but less than 75 meters (246 feet) in length is 1 nautical mile. The minimum range for a vessel 12 meters (39.4 feet) but less than 20 meters (65.6 feet) is .5 nautical miles.

Most every vessel is required to carry a sound-producing device, and even those who are not would do well to have one onboard. A vessel 12 meters (39.4 feet) or more in length must carry a whistle and a bell, while those 100 meters (328 feet) or more in length must additionally carry a gong.

 The bell and gong may be replaced by equipment having the same respective sound characteristics (an electronic loud hailer, for example) provided that manual sounding is always possible.

Vessels less than 12 meters (39.4 feet) in length are only required to carry an “efficient” sound-producing device, such as a bell, air horn or whistle. While banging on that galley pot may technically meet the letter of the law, do yourself (and everyone else) a favor and carry an appropriate sound-producing device.

Sound signals during restricted visibility

The below sound signals are applicable for recreational vessels during restricted visibility. Vessels engaged in other activities (towing, for example) will often have different or additional sound signal requirements. When in doubt, always refer to the USCG’s “Navigation Rules and Regulations Handbook.”

One prolonged blast: Power vessels underway through the water must sound one prolonged blast (4-6 seconds) at not more than 2-minute intervals.

Two prolonged blasts: A power vessel underway, but stopped (not making way) must sound two prolonged blasts roughly 2 seconds apart at intervals of not more than 2 minutes.

One prolonged blast plus two short blasts: A sailing vessel, a vessel not under command, restricted in her ability to maneuver or a vessel engaged in fishing (underway or at anchor) must sound three blasts in succession (one prolonged followed by two short blasts) at intervals of not more than 2 minutes,

Short blasts for 5 seconds: A vessel at anchor must ring a bell rapidly for about 5 seconds at intervals of not more than 1 minute apart. Vessels 100 meters or more in length (which require both a bell and a gong) also need to sound a gong in the after part of the vessel, after ringing the bell in the forepart.

One prolonged blast: A vessel nearing a bend or an area of a channel where other vessels may be obscured by an intervening obstruction must sound one prolonged blast. This signal must be answered with a prolonged blast by any approaching vessel that may be within hearing around the bend or behind the intervening obstruction.

While vessels less than 12 meters in length are not required to give the above signals, they are required to make some type of efficient sound signal at intervals not more than 2 minutes apart. While there is leeway regarding sound signals for vessels less than 12 meters, why try to reinvent the wheel here? Having a proper sound signaling device on smaller vessels and using the same sound signals (where practical) are a win/win for everyone on the water.