In response to FEPA Licence (33369/10/3, Supplementary Condition 9.36) for the Sheringham Shoal Offshore Wind Farm (OWF), underwater noise measurements were undertaken to assess underwater noise from the operational wind farm at ‘various frequencies across the sound spectrum, at a selection of locations immediately adjacent to and between turbines and within and outside the array at varying distances’. The underwater acoustic measurements performed at the operational Sheringham Shoal OWF, show that the radiated underwater sound from the particular wind turbines employed (Siemens SWT-3.6-107) is predominantly made up of tonal frequency components below around 500 Hz, resulting from the rotating nature of the turbine and its sub-components. Measurements were obtained in close proximity to individual wind turbines (~40 to 50m) for their full range of operating conditions, with snap-shot measurements at various positions between wind turbines and at a number of ranges away from the wind farm (ranging from about 50 m to 31 km), at all four compass points. The noise radiated from the operational wind turbines was typically comparable to or below the background noise level, and it was only certain frequency components that could be attributed to the operational wind turbines. The measured levels at the Sheringham Shoal OWF are comparable to those reported previously in the literature, where the same literature suggests that the underwater noise resulting from operational wind turbines would not be expected to result in injury to marine mammals and fish. The resultant noise levels in proximity to the turbines are also substantially lower than those expected to result in the onset of a permanent threshold shift in hearing response (PTS), or even a temporary threshold shift in hearing response (TTS), in marine mammals (Southall et al., 2007). It is also unlikely that these noise levels would result in a behavioural response, except perhaps in very close proximity to the turbines and only for species which might be sensitive to the tonal frequencies radiated.