Code of Federal Regulations Title 33. Navigation and Navigable Waters § 33.150.720 What are the requirements for sound signals?

The sound signal on each pumping platform complex must be operated whenever the visibility in any horizontal direction from the structure is less than 5 miles. If the platform is under construction, this requirement may be met by the use of a 2–second whistle blast, made every 20 seconds by a vessel moored at the platform.