Soundscape modelling in a marine area designated for floating offshore wind turbine (FOWT) development in northern Portugal

Environmental impact assessment and planning are crucial in offshore energy production, where underwater acoustics play a key role. As wind turbines generate energy, vibrations from moving components in the generator are also produced. These vibrations travel through the structure and are finally radiated to the underwater environment. Building on the FLOATFARM project, this study develops sound maps incorporating various anthropogenic sources for Viana do Castelo, Portugal, where floating offshore wind farms are planned. The Source Level of an individual floating wind turbine (FOWT) is estimated using Finite Element Analysis based on structural vibrations. Acoustic- structure interaction is considered, and radiated power is computed to calculate the acoustic Source Level. Underwater noise propagation is then modelled using blueOASIS’s RAINDROP, a tool that streamlines noise map creation. The model integrates site-specific bathymetry and AIS data to account for vessel contributions to the soundscape, alongside the windfarms and multiple FOWTs. Results include SPL levels around the wind farms at assumed different power generation conditions. Further advancements are needed in powertrain modelling and vibration and acoustic data validation. Nevertheless, this study proposes a framework for characterizing FOWT structure-borne noise and its underwater propagation, contributing to a more comprehensive understanding of offshore wind farm acoustics, even during project design stages.