NOISE REDUCTION
FEATURE SPONSOR
UNDERWATER NOISE REDUCTION
FOR MARINE LIFE PROTECTION Underwater noise reduction in the marine environment is one of the key indicators to achieve and maintain Good Environmental Status (GES) in European waters, in line with the requirements of Descriptor 11 (Introduction of Energy) of the Marine Strategy Framework Directive (MSFD, 2008/56/EC)
There are several contributors to marine noise generated by anthropogenic activities; since the MSFD came into force, the focus of noise reduction has been put into loud impulsive or intermittent noise sources that have the potential to cause significant damage to marine life. Loud anthropogenic noise sources include SONAR, explosives (particularly in relation to UXO removal), air-guns and pile-driving.
MINIMISING IMPACT As a result, governments have been demanding the implementation of strict mitigation measures to minimise the impacts of these activities and/or to restrict their schedule and extent whenever possible. The industry has responded by introducing innovative system to reduce noise levels either at the source or by introducing noise mitigation systems to reduce the
underwater noise propagating into the environment.
The offshore wind industry has led the way in the development of mechanisms and tools to drive down noise levels and has come up with solutions like suction buckets instead of traditional foundations and the blue hammer to cut noise at source and of systems that are deployed in the near or far-field to reduce the noise levels transmitted through the marine environment. The latter are examples of the most developed and widely implemented systems that are now applied regularly during the construction phases of large offshore windfarms, particularly in Germany where strict thresholds apply.
CHANGE OF FOCUS However, more recently the focus has started to move onto other
anthropogenic activities such as shipping, dredging and drilling that also generate underwater noise. Although these produce lower amplitudes, they are continuous noise sources that last for a long period of time.
Indeed, the IMO published MEPC.1/ Circ.833 Guidelines for the Reduction of Underwater Noise from Commercial Shipping to Address Adverse Impacts on Marine Life in 2014. Speed limits of 10knots for large ships are now being introduced (voluntary or mandatory) not only to avoid the risk of collision but also to reduce noise levels.
Baker Consultants
38
www.windenergynetwork.co.uk
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