The recent update of the HELCOM Baltic Sea Action Plan in has created an urgent need for reviewing the major sources of underwater noise, their known and likely impact on the marine environment and possible ways to mitigate the impact. Impulsive noise sources such as pile driving, seismic surveys, underwater explosions, low-frequency sonars etc. are known to cause negative effects in marine mammals and fish.

Mitigation includes: a) reduction in produced noise (source modification), b) reduction in radiated noise (abatement) and c) reduction in received noise (restriction of activities in sensitive areas and periods, deterrence from dangerous zones prior to impact).

Continuous low-frequency noise is predominantly generated by commercial vessels and recreational boating, with additional contribution from offshore infrastructure, e.g. renewables, oil and gas.

Mitigation measures are primarily source modification by improving design and operational procedures/speed reductio, and time/area restrictions including regional/local speed limits and/or requirements for vessels to abide by specific noise emission standards. Additional sources currently not monitored include echosounders and high frequency sonars, net pingers and seal scarers, and equipment other than air guns for exploring the uppermost layers of the seabed.

Read full report "MEASURES FOR REDUCTION OF ANTHROPOGENIC NOISE IN THE BALTIC" here.