Using Modelled Far-field Signatures of Airgun Arrays to Estimate Impact on Marine Mammals

We present a workflow to assess the risk of excessive sound exposure on marine mammals based on forward modelling of the far-field signatures from airgun arrays. The employed physical model takes into account the hydrodynamic effects around an airgun including the air bubble, directivity effects of realistic airgun arrays, and the interaction of the primary signals with the surface ghost reflection. Based on such signatures, we are calculating sound pressure and sound exposure levels as a function of distance and direction from the source, taking into account different geometrical spreading models. We also consider the frequency-dependent hearing threshold for different cetacean species. The workflow allows the estimation of a variety of different properties and scenarios in line with most recent regulatory requirements. Results can be used as a base for the planning of mitigation measures, such as exclusion radii around sensitive areas and soft-start procedures.