Mapping underwater noise for the Dutch part of North Sea (abstract)

The EU’s Marine Strategy Framework Directive (MSFD) requires member states (MS) to achieve or maintain Good Environmental Status (GES) by 2020. Specifically, the wording of Descriptor 11 requires “underwater noise to be at levels that do not adversely affect the marine environment”. The MSFD further requires monitoring of “trends in the ambient noise within the 1/3 octave bands 63 and 125 Hz (centre frequency)”. In the current study, we focussed on producing indicator maps for the Dutch North Sea for underwater sound of various natural
(wind, rain etc.) and anthropogenic (shipping, underwater explosions, seismic surveys and pile driving etc.) origins. The source properties and sound propagation are simulated by mathematical methods. It is our aim to generate noise maps for this particular geographical region that provide a clear indication of the average noise contribution from each source for different frequencies and receiver depths. Noise maps are presented for different sound sources, including surface ships and wind. Such maps can be used to investigate the impact of sound on marine mammals and fish. The spatial and temporal resolution of the noise maps and the frequency range can be tuned to different species by taking into account behaviour, distribution data, and speciesspecific hearing sensitivity. Collaboration between different scientific disciplines is needed to integrate noise maps with these different types of data. The end-product could become a valuable tool in making significantly better assessments of the impact of underwater noise on marine life.