In an effort to help customers manage disturbances to underwater marine operations, DNV has developed the industry’s first class notation for vessel-related noise: DNV Silent.
According to Einar Brubakk, DNV’s Head of Section for Noise & Vibration, the optional notation has been developed to help shipowners operating in different specialized segments to reduce safety and environmental risks caused by noise disturbances to sensitive acoustical instrumentation and marine life. “DNV Silent will enable research vessels, fishing trawlers and different types of offshore support vessels to operate more efficiently, avoid instrumentation malfunctions and minimize their acoustic impact on marine life,” he says.
While Brubakk acknowledges that at present, there are no regulations covering underwater noise, he notes that the IMO’s Marine Environmental Protection Committee (MEPC) has recently asked maritime nations to review their commercial fleets to identify the ships that contribute most to underwater noise pollution. “We believe that the IMO will consider legislation on this matter in the future,” he says. “In addition to helping our customers minimise risk related to vessel noise, the DNV Silent notation anticipates these regulations.”
Kai Abrahamsen, a principal engineer in DNV’s Noise and Vibration section says the project grew out DNV’s relationship with StatoilHydro. “StatoilHydro asked DNV to study the impact of vessel-related noise on sensitive acoustic instrumentation used in sub-sea installation communications,” he says. “After exhaustive testing, we concluded that while most vessel-related noise is related to propellers, diesel engines, generators, and water flow also contribute to underwater noise,” he says.
Abrahamsen explains that water is an efficient conductor of sound, and that engine and propulsion noise is amplified by a vessel’s hull. “The project helped us recognise a demand for a new optional notation which would allow shipowners serving offshore installations to minimize risks associated with underwater noise,” he says. “Fortunately, many of these issues can be managed cost-effectively, with optimum ship and component design.”
For operators pipe layers, seismic, dive support and offshore support vessels operating in and around subsea installations, DNV Silent will help differentiate their vessels from competitors by providing their customers with safer, quieter operations which minimise any harmful interference to sensitive acoustic equipment.
But Abrahamsen says that the notation applies to any vessel concerned about disturbing marine life. “DNV Silent has five sub-notations, including Acoustic, Seismic, Fishery, Research and Environmental,” he says. “The Research sub-notation was developed in line with ICES guidelines, which govern vessel-related noise for environmental research vessels. These guidelines are the toughest in the industry.”
In association with DNV Silent, the organization will offer sound radiation evaluation services and recommendations on hull, propulsion and engine design to reduce noise.
