Part D · Sound and light signals · Rule 32
Definitions
32(a) The word “whistle” means any sound signalling appliance capable of producing the prescribed blasts and which complies with the specifications in Annex III to these Regulations.
- “The word ‘whistle’ means any sound signalling appliance capable of producing the prescribed blasts”“Whistle” covers any sound signalling device, such as a horn or siren, that can make the short and prolonged blasts used in Rules 34 and 35. It needn’t be a whistle in the everyday sense.
- “and which complies with the specifications in Annex III to these Regulations”Annex III sets its pitch and loudness by vessel size: the larger the vessel, the lower the note (70 to 200 Hz at 200 metres or more; 250 to 700 Hz under 75 metres). A low, deep note usually means a large vessel.
A whistle is any sound signal device meeting Annex III. Vessels of 12 m or more must carry one (Rule 33(a)).
32(b) The term “short blast” means a blast of about one second’s duration.
- “The term ‘short blast’ means a blast of about one second’s duration”About one second. Short blasts are used for manoeuvring and warning signals (Rule 34): one short blast means “I am altering my course to starboard”.
Short blast: about 1 second.
32(c) The term “prolonged blast” means a blast of from four to six seconds’ duration.
- “The term ‘prolonged blast’ means a blast of from four to six seconds’ duration”From four to six seconds: not “about”, but within that range. Prolonged blasts are used in restricted visibility (Rule 35), for example one prolonged blast at least every 2 minutes for a power-driven vessel making way, and when approaching a bend (Rule 34(e)).
Prolonged blast: 4 to 6 seconds.
