Numerical simulations of hydro sound emissions due to offshore pile driving are presented in this paper. With the help of the finite element method (FEM) the propagation of sound waves evoked by a single hammer impact on an idealised monopile structure is simulated, taking into consideration the influence of ram energy and boundary conditions such as the seabed. The research presented in this paper investigates the possibility of a future prognosis of hydro sound emissions when offshore piles are driven into the ground. The aim is to develop technology that helps wind farms to be constructed without endangering noise-sensitive marine mammals.

1. Offshore Noise Emissions
1.1 Hydro sound as a consequence of impact driving

With the fast development of renewable energies and a growing awareness of ecological and sustainable issues, the wind energy industry has begun to reach for very rough and difficult, but promising regions to build new wind farms, particularly the vast and windy offshore areas surrounding the German coasts. In order to cope with enormous wind and wave loading, a pile foundation is, in most cases, chosen as the foundation system of a wind turbine. All loads have to be directed into the seabed with large steel piles which have to be driven into the seabed by means of impact hammers. Depending on the pile type, the diameter and especially the density of the subsoil, the impact energy is the most important factor in successfully driving the pile to its required depth. These oscillations lead to a sound pressure wave propagating in radial direction from the pile into the sea. Simultaneously, due to the dynamic reaction force at the pile toe, the seabed area close to the pile acts as a source of hydro sound, whose intensity is still a question of research.

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