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Ship Horn Signals and Their Meanings

Written by Anthony Roberts / Fact checked by Jonathan Larson

ship horn signals

Large and small vessels honking at the harbor and elsewhere are fascinating to watch and hear, but do we understand what these ship horn signals mean?

Sailors say one prolonged blast every two minutes signals a watercraft’s presence in hazy, cloudy, foggy, or other low-visibility situations.

One prolonged and two short blasts at two-minute intervals also indicate poor visibility for fishing boats, sailing vessels, and towing watercraft. These boat sound signals can also mean the absence of a commanding officer onboard, draft issues, or maneuverability concerns.

Learning the different sound signals for boats and ships helps boost boating safety by improving ship communication methods. It conveys one boater’s presence or intended action to others without “talking” to them.

Ship Horn Signals and Their Meanings

Watercraft operators must know how to interpret ship horn signals across situations. Nautical horn signals use short blasts lasting a second or 4- to 6-second prolonged blasts or a combination of both. Let’s look at these sound signals and appreciate their meanings.

1. Different Sound Patterns and Their Implications


Among many marine signals you must know as a boater, let’s start with the basic navigational sound codes using short and long blasts.

Sound Signal Meaning
One short blast The boater sounding the horn intends to pass another vessel on the port side.
Two short blasts The boater wants to pass another watercraft on the starboard side.
Three short blasts The boater tells other vessel operators the ship is reversing or “backing up.”
Five short blasts The boater “informs” another that he doesn’t understand the other’s intentions. It’s possible the sound from another vessel’s horn is confusing or doesn’t follow ship horn rules. Five short blasts are the universal sign for dangerous boat situations, telling other watercraft to move out of the way.
One prolonged blast The boater signals to other vessels that it’s leaving the slip or dock.
Two prolonged blasts every 2 minutes The ship is underway but not making any progress (it has stopped).

2. Combinations of Short and Long Blasts

The following marine sound signals chart combines prolonged and short horn blasts.

Sound Signal Meaning
1 long 1 short The vessel intends to pass under a bridge, signaling the bridge operator to raise the drawbridge.
1 long 2 short blasts every two minutes A sailboat is operating in poor visibility.
3 long 2 short blasts The boater is offering a “salute” or showing “deference” to another vessel.
7 short 1 long blasts This ship horn sound indicates a general emergency alarm. There could be onboard fire, grounding, collision, or other events requiring the crew to abandon the ship. The crew can also hear ships’ whistles or bell rings in some instances.

3. Horn Signals for Each Situation


Vessels must sound their horns using the correct ship horn codes only when they are within visual range of each other. Other conditions include a half-mile distance between the ships, and they are on course to crossing or meeting head-on.

Vessel operators must only use these sound signals in clear weather (i.e., not foggy nor hazy) for horn signals to be valid. In situations of poor visibility, ships must sound fog signals instead.

You might hear 3 long blasts, especially on cruise ships. Sailors disregard these sounds because they don’t mean anything. They are only for “show,” just as 5 long blasts on ships horn don’t exist in the rules.

4. Maneuvering, Warning, and Limited Visibility Signals


We already covered some ship horn rules related to maneuvering, warning, and limited visibility. The following sound signal patterns expand our understanding of boat sound signaling protocols. These codes will help you interpret Great Lakes freighter horn signals or any vessel.

Sound Signal Meaning
1 long blast every 2 minutes A power-driven vessel is traveling in limited visibility.
2 long + 1 short A power-driven watercraft wants to overtake another vessel on its right side on a narrow channel.
2 long + 2 short A power-driven watercraft wants to overtake another vessel on its left side on a narrow channel.
4 blasts (short) + interval + 1 short blast The vessel intends to turn at least 135 degrees starboard (right) side.
4 short + interval + 2 short blasts The ship wants to turn at least 135 degrees portside (left).

Requirements and Regulations on Ship Horn Signals

Here are other sound-signaling rules all boaters must know.

1. Based on Vessel Length


Watercraft shorter than 39.4 feet must have one sound-signaling device (i.e., air horn, whistle, or bell) to draw attention from other boaters in an emergency.

Boats between 39.4 and 65.6 feet must have two sound-signaling devices (i.e., a whistle and a bell). The whistle must produce a sound audible within half a nautical mile. Meanwhile, the bell must have a mouth diameter of not less than 7.87 inches.

2. When Do I Make Sound?

As mentioned, vessel operators should only make a sound with their horns or other sound-signaling devices when they are within the visual range of another boat (within half a mile). Moreover, basic horn signals only apply on clear days. Fog horn signals are necessary for low visibility conditions.


Mastering different ship horn signals is a crucial skill for vessel operators.

These non-verbal communication signs allow boaters to maneuver their watercraft safely while warning other vessels of their movements or ship status. Some horn signals are perfect for alerting other boaters of one’s presence in low-visibility situations.

It’s worth noting that some horn signals are uncommon, while a few don’t have meaning. Hence, boaters must distinguish legitimate sound signals from unsanctioned ones to ensure clear communication among boaters.

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