33 CFR §67.30-10

1. (a)The owner of a Class “C” structure shall install a sound signal if:
   1. (1)The structure is erected on or adjacent to the edge of a:
      1. (i)Navigable channel;
      2. (ii)Fairways; or
      3. (iii)Line of demarcation; and
   2. (2)The District Commander decides it is necessary for the safety of marine commerce.
2. (b)Sound signals required by paragraph (a) of this section must have rated range of at least one-half mile, unless the District Commander prescribes a greater rated range, not to exceed 2 miles.
3. (c)The owner of the structure shall operate the sound signal required by paragraph (a) of this section whenever the visibility in any direction is less than 3 miles, unless the District Commander establishes a greater or lesser distance of visibility, not to exceed 5 miles.
4. (d)Class “C” structures may have sound signals if:
   1. (1)Authorized by the District Commander under the provisions of Subpart 66.01 of this subchapter; and
   2. (2)The sound signal meets the requirements of § 67.10-1 (a) and (b).