COLREGs · Rule 32 · 33 CFR §83.32

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.

What does Rule 32 actually say?#

Source

Verbatim 33 CFR §83.32, public domain. The international COLREGs text is published by the IMO and cannot be reproduced here; this U.S. wording tracks it closely.

The word whistle means 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).

The term short blast means a blast of about 1 second's duration.

The term prolonged blast means a blast of from 4 to 6 seconds' duration.

Practice this rule#

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

Rule 32 — Sound Signal Definitions

Under both the International and Inland Rules, a 'short blast' is a blast of about ______.

Does Inland Rule 32 change anything?#

Inland Rule 32 is 33 CFR §83.32, reproduced above, and carries no exam-relevant divergence from COLREGs Rule 32. One answer serves both the International and the Inland version of a Rules of the Road question on this rule — which is worth knowing precisely because several neighbouring rules do not work that way.

21 of 38 rules differ somewhere; the five the exam leans on are Rule 9, Rule 10, Rule 24, Rule 28 and Rule 34, side by side on Inland vs International Rules.

Why it shows up on the exam#

Rule 32 defines the vocabulary that Rules 34 and 35 are written in. Learn the two durations cold — one second and four to six seconds — because every sound-signal question depends on them.

What does the exam actually test here?#

Whistle
A compliant sound-signalling appliance
The word 'whistle' means any sound-signalling appliance capable of producing the prescribed blasts and complying with the specifications in Annex III (33 CFR part 86).
Short blast
About 1 second
A short blast is a blast of about one second's duration. Rule 34 manoeuvring signals are built from these.
Prolonged blast
4 to 6 seconds
A prolonged blast is a blast of from four to six seconds' duration. Rule 35 fog signals and the Rule 34(e) bend signal use these. There is no such thing as a 'long blast' in the Rules.

Rule 32 — common exam questions#

How long is a short blast?

About one second's duration (33 CFR §83.32(b)).

How long is a prolonged blast?

From four to six seconds' duration (33 CFR §83.32(c)).

What counts as a whistle under the Rules?

Any sound-signalling appliance capable of producing the prescribed blasts and complying with the specifications in Annex III to the Rules, 33 CFR part 86 (33 CFR §83.32(a)).

Authoritative source#

33 CFR §83.32 — this section with its neighbours. 33 CFR Part 83 is public domain; checked 2026-05-16.
COLREGs Rule 32 is published by the IMO and is authoritative internationally.

Practise this rule against the real exam.

Real exam questions. No signup, no card.

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