Scaling Laws for Offshore Pile Driving Noise and Bathymetry Induced 3D Effects

The present thesis focuses on the investigation of the in?uence of bathymetry induced 3D e?ects on the sound levels and the derivation of simple to apply scaling laws for unmitigated as well as for mitigated pile driving scenarios. For this purpose, a hybrid pile driving noise model based on the ?nite element method and the Parabolic Equations (PE) is developed. The ?nite element model is used to derive the starting ?eld for the computationally more e?cient PE model, which is able to include horizontal di?raction and therefore allows for the investigation of bathymetry induced 3D e?ects. In addition, noise mitigation measures such as bubble curtains can be included in the model. The developed modelling approach is validated with measurement data from three di?erent wind farms including unmitigated and mitigated pile driving. The location of the occurrence of bathymetry induced 3D e?ects is investigated with data of three real-life scenarios with dedicated water depth pro?les. It is shown that sand dunes oriented in propagation direction are the main cause of 3D e?ects at the considered ranges. Furthermore, the in?uence of the sample size of the bathymetry data and the in?uence of uncertain acoustical parameters of the sea ?oor on the 3D e?ects are nvestigated and discussed. The modelling approach is used to derive scaling laws for the in?uence of the strike energy, the pile diameter, the ram weight, and the water depth on the sound exposure level and the peak sound pressure level. This is done for mitigated and unmitigated scenarios.