[Code of Federal Regulations]
[Title 33, Volume 1]
[Revised as of July 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 33CFR62.47]

[Page 149]
 
                TITLE 33--NAVIGATION AND NAVIGABLE WATERS
 
         CHAPTER I--COAST GUARD, DEPARTMENT OF HOMELAND SECURITY
 
PART 62--UNITED STATES AIDS TO NAVIGATION SYSTEM--Table of Contents
 
              Subpart B--The U.S. Aids to Navigation System
 
Sec. 62.47  Sound signals.

    (a) Often sound signals are located on or adjacent to aids to 
navigation. When visual signals are obscured, sound signals warn 
mariners of the proximity of danger.
    (1) Sound signals are distinguished by their tone and phase 
characteristics.
    (i) Tones are determined by the devices producing the sound (i.e., 
diaphones, diaphragm horns, reed horns, sirens, whistles, bells and 
gongs).
    (ii) Phase characteristics are defined by the signal's sound 
pattern, i.e., the number of blasts and silent periods per minute and 
their durations. Sound signals emanating from fixed structures generally 
produce a specific number of blasts and silent periods each minute when 
operating. Buoy sound signals are generally actuated by the motion of 
the sea and therefore do not emit a regular signal characteristic.
    (2) Where no live watch is maintained, sound signals are normally 
operated continuously. However, some are equipped with fog detectors 
which activate sound signals when visibility falls below a predetermined 
limit.
    (b) Mariners should not rely solely on sound signals to determine 
their positions for the following reasons:
    (1) Distance cannot be accurately determined by sound intensity.
    (2) Occasionally sound signals may not be heard in areas close to 
their location.
    (3) Signals may not sound in cases where fog exists close to, but 
not at, the location of the sound signal.
    (4) As buoy signals are generally activated by sea motion, they may 
produce no signals when seas are calm.
    (5) As previously noted, buoy positions are not always reliable. 
Therefore their sound signals cannot be assumed to be emanating from a 
fixed position.