Every sound signal, to listen to.

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 📢Whistle

   Whistle: required on every vessel of 12 m or more. It produces the prescribed short and prolonged blasts (Annex III).

2. 🔔Bell

   Bell: required in addition on vessels of 20 m or more.

3. Gong

   Gong: required in addition on vessels of 100 m or more; its tone must not be confused with that of the bell.

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 🔊Sound

   Some other means of making an efficient sound signal, for example a portable horn, sufficient to be heard by other vessels.

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 📢Whistle

   One short blast: "I am altering my course to starboard."

2. 📢Whistle

   Two short blasts: "I am altering my course to port."

3. 📢Whistle

   Three short blasts: "I am operating astern propulsion."

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 📢Whistle

   Two prolonged + one short: "I intend to overtake you on your starboard side."

2. 📢Whistle

   Two prolonged + two short: "I intend to overtake you on your port side."

3. 📢Whistle

   Prolonged–short–prolonged–short, the overtaken vessel’s agreement.

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 📢Whistle

   At least five short and rapid blasts: doubt. The vessel sounding it does not understand the other’s intentions, or doubts that she is taking enough action to avoid collision.

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 📢Whistle

   One prolonged blast, sounded by a vessel nearing a bend or an obstruction that hides other vessels.

2. 📢Whistle

   One prolonged blast in answer, given by any approaching vessel within hearing around the bend or behind the obstruction.

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 📢Whistle

   One prolonged blast at intervals of not more than 2 minutes: a power-driven vessel making way through the water.

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 📢Whistle

   Two prolonged blasts about 2 s apart, at intervals of not more than 2 minutes: a power-driven vessel underway but stopped and making no way.

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 📢Whistle

   One prolonged + two short, at intervals of not more than 2 minutes: NUC, RAM, constrained by draught, sailing, fishing, or towing/pushing.

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 📢Whistle

   One prolonged + two short, at intervals of not more than 2 minutes: a vessel fishing at anchor, or a RAM vessel working at anchor (instead of the anchor bell).

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 📢Whistle

   One prolonged + three short, at intervals of not more than 2 minutes: a manned vessel being towed, made just after the towing vessel’s signal.

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 📢Whistle

   Treated as one power-driven vessel: it gives the paragraph (a) signal when making way (or the paragraph (b) signal when stopped).

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 🔔Bell

   Bell rung rapidly for about 5 seconds, every minute: a vessel at anchor.

2. 🔔Bell + Gong

   Vessel of 100 m or more: the bell forward, immediately followed by the gong sounded rapidly aft.

3. 📢Whistle

   One short, one prolonged, one short: an optional whistle signal to warn an approaching vessel of her position.

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 🔔Bell

   Three distinct strokes, the rapid 5-second ringing, then three distinct strokes again: a vessel aground.

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 🔊Sound

   Some other efficient sound signal at intervals of not more than 2 minutes: a vessel of 12 to 20 m that does not give the anchor or aground bell signals.

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 🔊Sound

   Some other efficient sound signal at intervals of not more than 2 minutes: where the prescribed appliances are not carried.

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 📢Whistle

   Four short blasts: an optional identity signal for a pilot vessel on pilotage duty.

Played at true length: a short blast lasts about 1 second and a prolonged blast 4 to 6 seconds (Rule 32). Here a prolonged blast plays for 5 seconds.

1. 🔊Sound

   A gun or other explosive signal fired at intervals of about a minute.

2. 🔊Sound

   A continuous sounding with any fog-signalling apparatus.

3. 📢Whistle

   The group · · · – – – · · · (SOS) in the Morse Code, made by any signalling method. A Morse dash is three times the length of a dot, not a prolonged blast.