Mitigation of offshore piling noise

Offshore application of Hydro Sound Dampers (HSD)

Company / Unternehmen: TU Braunschweig, Institut für Grundbau und Bodenmechanik
Speaker / Referent: Benedikt Bruns
Position: Wissenschaftlicher Mitarbeiter

Pile driving by hydraulic impact hammers during the installation of offshore wind foundations induces considerable hydro sound that is radiated from the piles into the surrounding water. These very high underwater noise emissions are potentially harmful to marine mammals such as harbor porpoises, harbor seals or grey seals. The BSH set the maximum allowed underwater sound level to 160 dB (SEL) at a distance of 750 m away from pile driving to protect the marine life. A new underwater piling noise mitigation system using so called hydro sound dampers (HSD) is developed to reach the target given by the BSH. The method of HSD is a very promising new method to reduce underwater sound by scattering, dissipation and resonant effects.
Developments, laboratory tests, large scale tests and offshore tests of HSD-systems are carried out at the Institute of Soil Mechanics and Foundation Engineering at the Technische Universität Braunschweig within research projects of the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) together with several companies of the offshore wind industry.

The results of the different measurements are very promising. One of the main advantages of HSD is that the sound mitigation can be adjusted to a predefined frequency ranges. Large scale tests in a wave flume result in noise reductions between 25 and 30 dB of sweep excitations of underwater noise. First offshore tests already show noise reductions due to the HSD-system of about 23 dB within the important frequency ranges between 100 Hz and 700 Hz, using HSD-elements of different materials. Also the results of the following offshore test “London Array” in August 2012 with different types of HSD-elements will be presented. Within this testing also vibration measurements on the seabed while pile driving was done. All this results are very interesting and important for upcoming wind farms. Further tests and applications are planned in 2013.