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COLREGs · Rule 32

Sound Signal Definitions

Defines whistle, short blast (≈1 sec), and prolonged blast (4–6 sec). 'Whistle' includes any sound-signalling appliance capable of producing the prescribed blasts.

Source: 33 CFR §83.32 · COLREGs Rule 32Last verified 2026-05-16

Rule text#

Source

The international COLREGs text is published by the IMO and is not available to reproduce here. Shown below is the U.S. counterpart, 33 CFR §83.32, which tracks the international wording closely.

(a)The wordmeans any sound signaling appliance capable of producing the prescribed blasts and which complies with specifications in Annex III to these Rules (33 CFR part 86).

(b)The termmeans a blast of about 1 second's duration.

(c)The termmeans a blast of from 4 to 6 seconds' duration.

Authoritative source#

Source links checked against the current public rule corpus on 2026-05-16.

  • 33 CFR §83.32 — the section this text comes from, with its neighbours.
  • International COLREGs Rule 32 verbatim text is published by the IMO and is authoritative for international waters.

Practice this rule#

One real exam question on this rule, cited to source. No sign-up.

A 'short blast' on a whistle is a blast of ______.

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COLREGs Rule 32: Sound Signal Definitions — Captain's Exam Prep · CaptainsGround