Section 67.20-10 - Sound signal(a) The owner of a Class "A" structure shall:(1) Install a sound signal that has a rated range of at least 2 miles; and,(2) Operate the sound signal when the visibility in any direction is less than 5 miles.(b) The District Commander may waive any requirements in paragraph (a) of this section if he or she finds that a structure is so close to other structures and so enveloped by the sound signals on other structures that it is not a hazard to navigation.CGD 72-74R, 37 FR 13513, July 8, 1972, as amended by USCG-2001-10714, 69 FR 24984 , May 5, 2004