This project has been undertaken by Subacoustech Environmental Ltd for DONG Energy. It describes a series of underwater noise measurements at the Gunfleet Sands Offshore Wind Farm site during installation of monopile foundations. Herring are known to spawn in the Blackwater River region to the west of the wind farm site and some concerns over the potential impact that the underwater noise might have on migrating and spawning herring were raised. The primary aim of the measurements was to measure the levels of underwater noise from impact piling operations at a location where herring had been found to be spawning on the same day. This would enable cause and effect to be established.