immediate area through bubble oscillation although this would not be expected to be a dominant component of the overall ambient noise. Biological contribution to ambient noise can be significant depending on the location and time. These sounds can include a variety of marine mammal vocalisations spanning from a few hertz to several tens of kilohertz and include lower frequency sounds made by fish (Richardson et al. 1995; Amorim 2006).
24.
The primary anthropogenic contributors to the ambient noise level in the North Sea include shipping (e.g., fishing, cargo, cruise ship, ferries, and aggregate extraction) and oil and gas related activities. Some of the vessels operating in and around East Anglia THREE, depending on vessel speed, size, type, age and condition etc., may generate significant noise levels, with the literature indicating maximum TOB source level of over 200dB re 1 μPa·m (Malme et al. 1989) for a large tanker, over 186dB re 1 μPa·m for a cargo vessel (Arveson and Vedittis 2000) and over 170dB re 1 μPa·m for a passenger ferry (Malme et al. 1989) (for the TOB where the source level is maximum). These would generally be expected to result in noise levels above ambient levels out to distances of several km and local ship traffic would influence the ambient noise to an extent. However, these would be localised, short term changes and the more constant contributor to noise within East Anglia THREE would be distant shipping.
25. Dredging vessels could also be a source of noise, which may be noisier at higher frequencies than commercial vessels operating in the shipping lanes (Robinson et al. 2011). There are no licensed or active dredging areas within the East Anglia Zone, although, a number of Active Dredge Zones, Dredging Application Option and Prospecting Areas (DAOPAs), and Production Agreement Areas exist to the southwest and further to the north and northwest of the East Anglia Zone (The Crown Estate 2014). It could be assumed that, at ranges of several km (>10km), these may be too far away to considerably contribute to an increase in ambient noise, above existing shipping noise, around East Anglia THREE.
26.
The southern North Sea supports a concentration of oil and mostly gas fields, which are concentrated mostly to the north of the East Anglia Zone (DECC 2014), which if operational may radiate low frequency machinery noise and general broadband noise into the water that could potentially influence ambient noise trends in the North Sea and the southern North Sea area. Whilst oil and gas activity in the UK Continental Shelf quadrants immediately adjacent to East Anglia THREE may contribute to ambient noise, the ambient noise around East Anglia THREE would likely be dominated by local shipping and sea-state.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm Appendix 9.1 Underwater Noise Modelling 7
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