33 CFR 83.33: Sound signal equipment by vessel length
Last reviewed: November 2, 2026
This section says what sound signal equipment a vessel must carry, based on its length. Vessels of 12 meters or more need a whistle, vessels of 20 meters or more add a bell, and vessels of 100 meters or more add a gong. A vessel of less than 12 meters that does not carry these appliances must have some other means of making an efficient sound signal.
Applies toVessels, with the equipment required depending on whether the vessel is less than 12 meters, 12 meters or more, 20 meters or more, or 100 meters or more in length.
What it says
A vessel of 12 meters or more in length must be provided with a whistle.
33 CFR 83.33(a)“A vessel of 12 meters or more in length shall be provided with a whistle”
A vessel of 20 meters or more in length must be provided with a bell in addition to a whistle.
33 CFR 83.33(a)“a vessel of 20 meters or more in length shall be provided with a bell in addition to a whistle”
A vessel of 100 meters or more in length must also be provided with a gong, whose tone and sound cannot be confused with that of the bell.
33 CFR 83.33(a)“a vessel of 100 meters or more in length shall, in addition, be provided with a gong, the tone and sound of which cannot be confused with that of the bell”
The whistle, bell and gong must comply with the specifications in Annex III to these Rules (33 CFR part 86).
33 CFR 83.33(a)“The whistle, bell and gong shall comply with the specifications in Annex III to these Rules (33 CFR part 86).”
The bell or gong or both may be replaced by other equipment having the same respective sound characteristics, provided that manual sounding of the prescribed signals must always be possible.
33 CFR 83.33(a)“The bell or gong or both may be replaced by other equipment having the same respective sound characteristics, provided that manual sounding of the prescribed signals shall always be possible.”
A vessel of less than 12 meters in length is not obliged to carry the sound signaling appliances prescribed in paragraph (a), but if it does not carry them, it must be provided with some other means of making an efficient sound signal.
33 CFR 83.33(b)“but if she does not, she shall be provided with some other means of making an efficient sound signal.”
Common questions
Does a vessel under 12 meters need a whistle?
A vessel of less than 12 meters is not obliged to carry the paragraph (a) appliances. If it does not carry them, it must be provided with some other means of making an efficient sound signal.
“but if she does not, she shall be provided with some other means of making an efficient sound signal.”
When does a vessel need a bell as well as a whistle?
A vessel of 20 meters or more in length must have a bell in addition to a whistle.
“a vessel of 20 meters or more in length shall be provided with a bell in addition to a whistle”
Can a bell or gong be replaced by other equipment?
Yes. The bell or gong or both may be replaced by other equipment having the same respective sound characteristics, provided manual sounding of the prescribed signals is always possible.
“The bell or gong or both may be replaced by other equipment having the same respective sound characteristics”
Which vessels must carry a gong?
A vessel of 100 meters or more in length must, in addition, be provided with a gong that cannot be confused with the bell.
“a vessel of 100 meters or more in length shall, in addition, be provided with a gong”
The text of 33 CFR 83.33
Electronic Code of Federal Regulations (eCFR), current as of April 16, 2026 · Read it on eCFR
Equipment for sound signals (Rule 33)
(a) A vessel of 12 meters or more in length shall be provided with a whistle, a vessel of 20 meters or more in length shall be provided with a bell in addition to a whistle, and a vessel of 100 meters or more in length shall, in addition, be provided with a gong, the tone and sound of which cannot be confused with that of the bell. The whistle, bell and gong shall comply with the specifications in Annex III to these Rules (33 CFR part 86). The bell or gong or both may be replaced by other equipment having the same respective sound characteristics, provided that manual sounding of the prescribed signals shall always be possible.
(b) A vessel of less than 12 meters in length shall not be obliged to carry the sound signaling appliances prescribed in paragraph (a) of this Rule but if she does not, she shall be provided with some other means of making an efficient sound signal.
Sections it refers to
- 33 CFR part 86
The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of April 16, 2026. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.