Assessment of acoustic emissions of off-shore wind farms

DEWI has performed the research study “Standards for the assessment of acoustic emissions of off-shore wind farms”.

The influences that the planned off-shore wind farms in the North Sea and in the Baltic Sea will have on the marine environment are being investigated in a number of research projects carried out on behalf of the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety. Within this framework, the institutes DEWI, ITAP and ISD are carrying out a research project of several years' duration investigating the additional acoustic impact to be expected from the construction activities and from the operation of the wind farms planned. The project will also supply a reliable data basis for biological investigations of the sense of hearing of harbour porpoises and seals carried out at the same time.

Another aim of this project is the standardisation of the measuring and evaluation procedures. Especially in acoustics, marginal differences in the investigation methods can already have drastic effects on the results obtained. Among the objects investigated are off-shore wind turbines in other countries that have already been operating for several years, as well as construction activities in the off-shore area.

The research project also includes the development of prediction models allowing to estimate the noise impact on the marine environment even before a wind farm is realised. This is important to be able to intervene at an early stage and modify the turbine design or wind farm layout, if necessary. Accompanying the project, a working group consisting of biologists, regulatory authorities, experts from industry and acoustic experts was established in order to develop a basis for the definition of thresholds for acoustic noise immissions.

The research project was prolonged mid-2004 in order to complete the acoustic data basis and thus make the proposed prediction methods more reliable. Because of the high acoustic noise levels measured during construction activities, means to reduce noise will also be investigated more closely. In co-operation with companies specialising in this subject, practicable measures were be discussed, calculated and tested on real objects. Another focal point is the definition of the propagation damping decisive for the range of impact of the acoustic noise immissions.