Numerical investigation of the influence of different sound mitigation systems on the underwater sound pressure level due to offshore pile driving
Wind energy plays a key role for the turnaround of the German energy policy. In addition to onshore capacities, offshore wind parks get more and more important. To erect offshore wind turbines, huge steel piles are driven up to 40m into the soil by impact hammers. This construction technology is accompanied by massive underwater noise impacts. To protect the marine wildlife, e.g. the harbor porpoise, limiting values have been introduced by the German authorities. In most cases it is hard to comply with these limiting values without applying special sound damping measures. The sound mitigation systems, which are in practical use today, can be distinguished with respect to their distance to the pile. On the one hand, systems in the direct vicinity of the pile are used to mitigate the underwater sound pressure, e.g. cofferdams or small bubble curtains. On the other hand, systems are used, which reduce the acoustic pressure wave in larger distances to the pile. In the present contribution, the different influence of several sound mitigation systems on the underwater sound pressure level is evaluated with a numerical model. The modeling strategy is discussed and representative results are presented.