Offshore wind turbine noise propagation and the "ground effect" of the sea: a comparison of Effective Flow Resistivity (EFR) of still and moving water surfaces

With the proliferation of Offshore Wind Turbine (OWT) development, the potential annoyance problems caused onshore from long range propagation of noise over the sea surface generated by the turbines must be investigated thoroughly. Measurement of the Ground Effect in relation to the sea surface is onerous and under-researched. In this suite of experiments, a method similar to that described in ANSI S1.18-1999 "Template method for Ground Impedance" is used to compare the differences in effective flow resistivity (EFR) between water surfaces that have 1) a surface that is still, 2) gravity waves that move in the direction of the noise propagation 3) gravity waves that flow opposite the direction of noise propagation. These results are further compared to standard surfaces such as soil and concrete. The frequency response of the surface under these different scaled-down surface gravity wave conditions may provide some insight into the behaviour of lower frequencies over the large scale surface wave conditions at sea.