Washington State Ferries Underwater Noise Study
NCE performed an underwater noise study for Washington State Ferries (WSF) which included the measurement of nine vessels representing all seven of WSF’s operating classes. The study quantified noise, potential impacts to orcas and other marine life, and methods of reducing noise. NCE utilized long-term acoustic monitors to perform vessel noise measurements in general accordance with ANSI S12.64 while allowing the vessels to maintain their normal operating schedule. Simultaneously, vessel operational and environmental data were collected allowing for assessments of noise at varying propeller RPMs, operating powers, and speeds. This information was compiled into a database which was used to calculate source levels and identify impacts to marine life using National Marine Fisheries Service (NMFS) guidelines. The measurement data was also used to identify causes of noise ranging from propeller cavitation to specific machinery items. NCE’s decades of experience in quiet ship design was used to identify potential methods of reducing underwater noise.