Structure-Borne Wave Radiation by Impact and Vibratory Piling in Offshore Installations: From Sound Prediction to Auditory Damage

Anthropogenic noise emission in the marine environment is a key issue nowadays and has drawn the attention of regulatory bodies in various nations. In particular, the noise generated during the installation of foundation piles for the offshore wind industry is considered to be harmful for aquatic species. A reliable prediction of the underwater noise during the installation of a foundation pile is thus essential for the proper assessment of the ecological impact. In this paper, the structure-borne wave radiation is investigated with the help of a semi-analytical model for two cases. The first case considers a pile that is installed with the help of an impact hammer, whereas the second one deals with a pile that is driven into the seabed with the help of a vibratory device. The spatial distribution and the frequency content of the radiated sound are analyzed, and the differences are highlighted between the two cases. The model is validated with data available in the literature that were collected during several measurement campaigns. Subsequently, the predicted noise levels are converted into an equivalent index that reflects the auditory damage to certain marine species, and a method is presented for the derivation of zones of impact around the pile that are based on the noise predictions by the models and the chosen method of installation. This approach can be used to define critical zones within which a predefined level of auditory damage is to be expected based on a specific installation scenario.