A whistle on a vessel shall provide, in the direction of the forward axis of the whistle and at a distance of 1 meter from it, a sound pressure level in at least one 1/3 -octave band of not less than the appropriate figure given in Table 86.05 within the following frequency ranges (±1 percent):
(a) 130-1200 Hz, for a vessel 75 meters or more in length;
(b) 250-1600 Hz, for a vessel 20 meters but less than 75 meters in length;
(c) 250-2100 Hz, for a vessel 12 meters but less than 20 meters in length.
Length of vessel in meters
Fundamental frequency range (Hz)
For measured frequencies (Hz)
1/3-octave band level at 1 meter in dB referred to 2×10 −5 N/m2
Audibility range in nautical miles
200 or more
75 but less than 200
20 but less than 75
12 but less than 20
Note. The range of audibility in the table above is for information and is approximately the range at which a whistle may usually be heard on its forward axis in conditions of still air on board a vessel having average background noise level at the listening posts (taken to be 68 dB in the octave band centered on 250 Hz and 63 dB in the octave band centered on 500 Hz).
In practice the range at which a whistle may be heard is extremely variable and depends critically on weather conditions; the values given can be regarded as typical but under conditions of strong wind or high ambient noise level at the listening post the range may be much reduced.
Title 33 published on 2012-07-01
no entries appear in the Federal Register after this date.
This is a list of United States Code sections, Statutes at Large, Public Laws, and Presidential Documents, which provide rulemaking authority for this CFR Part.