Offshore wind farms (OWF) will soon contribute to significant growth in the renewable energy sector. At present just a few OWF have been built. As of 2012, Germany has an offshore wind capacity of little more than 200 MW, whereas Denmark has already reached 875 MW and the UK soon will reach 2.000 MW. There are plans for another 114 GW in EU countries, with a cumulative investment of 211 billion Euro. This expansion of offshore wind energy needs to be organized in a sustainable way. The Habitat Directive has to be considered in each European country in the same way. Currently, the environmental impacts of the underwater noise on porpoises, caused by jack-hammers that are mostly used to drive the pile foundations into the seabed, are assessed differently amongst the forerunners of offshore wind energy like Denmark, Great Britain, and Germany. This paper includes an overview of the possible applied measures for avoiding damages, as well as obligatory measures and the different thresholds of European countries. The analysis concludes by identifying a need for international standardization. The paper is result of research as part of the PhD thesis "Strategies for Sustainable Development of Offshore Wind Energy" of the author.