Studies have indicated that commercial ships are the dominant source of noise in most coastal areas of the Northern Hemisphere. These areas are important habitats for many marine mammals, such as baleen whales, seals and sea lions who are particularly vulnerable to impacts from incidental shipping noise because they produce and perceive low-frequency sounds.
The noisiest merchant ships have one thing in common: cavitation associated with their propellers. Both propeller design and wake-flow into the propeller contribute to cavitation.
New ABS-classed ships are being designed to minimize ship-radiated noise with the help of model tests and advanced CFD analyses.
For existing ships, modifications can be made to a ship’s propeller to reduce hydro-acoustic noise and improve operational efficiency. Wake-equalizing ducts may also be added to improve propeller wake flow.