Part D — Sound and light signals
COLREGs Rule 32: Definitions of sound signals
Rule 32 defines the sound signals: a short blast lasts about one second and a prolonged blast lasts four to six seconds. A 'whistle' is any device that can produce them.
What Rule 32 says
- A whistle is any sound signalling appliance able to produce the prescribed blasts and meeting Annex III.
- A short blast is a blast of about one second's duration.
- A prolonged blast is a blast of four to six seconds' duration.
This is a plain-English summary, not the official wording. For the exact text, see the IMO convention. In UK waters the rules are given legal force by the Merchant Shipping (Distress Signals and Prevention of Collisions) Regulations.
What it means on a yacht
A yacht's air horn counts as a whistle. Count 'one thousand' for a short blast and to five for a prolonged one.
Practise it
Test yourself on who gives way in the free COLREGs trainer, or print the rules of the road cheat sheets for the chart table.