A short blast lasts about one second, a prolonged blast from four to six. That single difference separates "I am altering course to starboard" from "I am approaching a blind bend". Press listen on any row and you hear the real timing, in three pitches: a deep 70 to 200 Hz whistle for vessels of 200 metres and over, a mid 130 to 350 Hz one, and a high 250 to 700 Hz horn for small craft.
The page covers manoeuvring and warning signals of rule 34 (including five short and rapid blasts, the doubt signal), the fog signals of rule 35 at intervals of not more than two minutes, the bell and gong of a vessel at anchor or aground, the equipment required by rule 33 and the distress signals of rule 37.
Read the underlying rules on the rules page, see who shows which lights on the lights and shapes page, or drill the signals by ear with the flashcards.
The sound is synthesised in your browser to Annex III of the COLREGs: a short blast lasts about 1 second, a prolonged one 4 to 6, so long signals really do take that long. Nothing is downloaded; you need speakers or headphones.
Manoeuvring and warning signals · rule 34
Fog · rule 35 · intervals of not more than 2 minutes
Equipment and distress · rules 32, 33, 36, 37
All 38 rules, one page each
- Rule 1 Where the rules apply
- Rule 2 Responsibility and the right to depart from the rules
- Rule 3 Who is called what
- Rule 4 This section applies in any visibility
- Rule 5 Look-out
- Rule 6 Safe speed
- Rule 7 Risk of collision
- Rule 8 How to manoeuvre so you are understood
- Rule 9 Narrow channels
- Rule 10 Traffic separation schemes
- Rule 11 When this section applies
- Rule 12 Sailing vessel against sailing vessel
- Rule 13 Overtaking
- Rule 14 Head-on situation
- Rule 15 Crossing situation
- Rule 16 Action by the give-way vessel
- Rule 17 Action by the stand-on vessel
- Rule 18 Responsibilities between vessels
- Rule 19 Conduct of vessels in restricted visibility
- Rule 20 When each is shown
- Rule 21 The kinds of light
- Rule 22 Ranges at which the lights must be visible
- Rule 23 Lights of a power-driven vessel underway
- Rule 24 Towing and pushing
- Rule 25 Sailing vessels and vessels under oars
- Rule 26 Fishing vessels
- Rule 27 Not under command, restricted in ability to manoeuvre, divers, mine clearance
- Rule 28 Constrained by draught
- Rule 29 Pilot vessels
- Rule 30 Anchored and aground
- Rule 31 Seaplanes and WIG craft
- Rule 32 Short and prolonged
- Rule 33 What must be carried
- Rule 34 Manoeuvring and warning signals
- Rule 35 Sound signals in fog
- Rule 36 Signals to attract attention
- Rule 37 Distress signals
- Rule 38 Who got a delay and for how long
Sound signal terms: what each blast is called
Rules 32 to 35 name the sounds and set their length. These are the words used in the list above.
Whistleship's horn, siren
Any sound signalling appliance able to produce the prescribed blasts and meeting Annex III. Pitch depends on length: 70-200 Hz for 200 m and over, 130-350 Hz for 75-200 m, 250-700 Hz under 20 m.
Short blastone second blast
A blast of about one second. One, two or three short blasts are the manoeuvring signals of rule 34: altering to starboard, altering to port, operating astern propulsion.
Prolonged blastlong blast
A blast of four to six seconds. One prolonged blast every two minutes is a power-driven vessel making way in fog, and one prolonged blast is also the signal on approaching a blind bend.
Manoeuvring signalsrule 34 signals
Given in sight of one another by a power-driven vessel underway: one short for starboard, two short for port, three short for astern propulsion. They may be backed up by white light flashes of the same pattern.
Doubt signalfive short blasts, wake-up signal
At least five short and rapid blasts, meaning «I do not understand your intentions» or «I doubt you are taking enough action to avoid collision». May be backed up by five or more rapid flashes.
Bend signalblind bend signal
One prolonged blast sounded on nearing a bend or an obstruction where other vessels may be hidden. Any vessel hearing it round the bend answers with one prolonged blast.
Fog signalsrestricted visibility signals
Sounded in or near restricted visibility, by day and night, at intervals of not more than two minutes: one prolonged for making way, two prolonged for stopped, one prolonged and two short for the special categories of rule 35 (c).
Bell and gonganchor signals
A vessel of 20 m and over carries a bell, of 100 m and over also a gong. At anchor in fog: rapid ringing of the bell for about 5 seconds every minute; over 100 m, the gong follows in the after part. Aground: three separate strokes before and after the ringing.