Rule 32 — Definitions
Three definitions that every sound signal in Part D is built from. Get the two blast lengths right and the signals in Rules 34 and 35 come down to counting. What Rule 32 says, what Annex III adds about the whistle itself, and how it comes up in an MCA oral.
It defines three terms used in Part D (Sound and light signals).
Rule 32(a): a whistle is any sound signalling appliance 'capable of producing the prescribed blasts' that complies with the specifications in Annex III.
Rule 32(b): a short blast lasts about one second.
Rule 32(c): a prolonged blast lasts 'from four to six seconds'.
No. Rule 32(a) defines a whistle by what it does, not by what it is: any sound signalling appliance that can produce the prescribed blasts and meets Annex III. As we read it, an air or electric horn that meets Annex III is a whistle for the purposes of the rules.
Because most sound signals in the rules are combinations of short and prolonged blasts, and the combination is the message. One short blast under Rule 34(a) means 'I am altering my course to starboard'; one prolonged blast under Rule 35(a) is a power-driven vessel making way in restricted visibility. In practice, a prolonged blast cut short can be heard as a short one, and the signal becomes a different signal.
About one second (Rule 32(b)). The rule says 'about', so it is not a precise figure. In practice, give a distinct blast of about a second, not a brief toot that may not be heard as a signal.
Four to six seconds (Rule 32(c)). It is a range, not a single figure: anything from four to six seconds is a prolonged blast.
The phrase appears in Rule 34(d), the doubt signal: 'at least five short and rapid blasts'. Rule 32 does not define it separately. As we read it, they are short blasts given in quick succession, so the signal cannot be confused with the one, two or three short blasts of Rule 34(a).
No — only the whistle and the two kinds of blast. Rule 33 sets which vessels must carry a bell and a gong, Annex III sets their specification, and Rule 35(g) and (h) say how they are used at anchor and aground: the bell rung rapidly for about five seconds, the gong sounded rapidly for about five seconds after it on a vessel of 100 metres or more.
Annex III 1(a): the fundamental frequency lies within 70–700 Hz. Annex III 1(b) narrows it by length, 'to ensure a wide variety of whistle characteristics': 70–200 Hz for a vessel of 200 metres or more; 130–350 Hz for 75 metres but less than 200 metres; 250–700 Hz for less than 75 metres.
The permitted band moves lower as the vessel gets bigger, but the bands overlap, so pitch is a rough guide to size, not a measure of it.
Annex III 1(c) gives audibility ranges by length, 'for information': 2 nautical miles for a vessel of 200 metres or more; 1.5 for 75 metres but less than 200 metres; 1 for 20 metres but less than 75 metres; 0.5 for less than 20 metres.
Annex III also warns that in practice the range is 'extremely variable' and depends critically on the weather, and that strong wind or high background noise at the listening post may much reduce it. In practice, a signal you have sounded is not a signal the other vessel has heard.
Annex III 1(e): as high as practicable, to reduce interception of the sound by obstructions and the risk of hearing damage to the crew. A directional whistle used as the vessel's only whistle is installed with its maximum intensity directed straight ahead.
It may come up as the first step of a sound-signal question. Examples of the kind of question to be ready for:
“How long is a prolonged blast? And a short blast?”
“What is a whistle, as the rules define it?”
“Roughly how far should the whistle of a 50-metre yacht be heard?”
“Why does the length of the blast matter?”
The common slips: giving one figure for a prolonged blast instead of the four-to-six-second range; sounding a prolonged blast so short it could be taken for a short one; and treating the Annex III audibility ranges as a promise rather than a figure for still air.
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