133. Although the previous studies generally indicate that there is unlikely to be any significant impact on marine mammals, operational noise from the wind turbines would be present for the operational life of the windfarm and will contribute to the ambient noise within the windfarm Whilst the actual radiated broadband noise levels are relatively low, the potential increase in local ambient noise may influence species which are present in the area that may be affected by increasing ambient noise levels.
134. Although the effect on fish response is more difficult to establish given the lack of information available in the scientific literature, there is indicative evidence that fish would be unlikely to show significant avoidance to the broadband noise levels radiating from the turbine. The International Council for the Exploration of the Sea (ICES) has formulated recommendations for maximum radiated underwater noise from research vessels which are approximately 30dB above the hearing threshold of Atlantic cod and herring (ICES:209 1995). The implication of this is that the presence of continuous noise that is not significantly above the hearing threshold of fish is not thought to cause any significant movement of fish away from the source. In studies of very low frequency sound, Sand et al. (2001) indicate that consistent deterrence from the source is only likely to occur at particle accelerations equivalent to a free- field SPL of 160dB re 1 μPa (RMS). This is higher than the noise levels reported in the open literature for operational windfarms measured at a number of ranges, all within a few hundred m of the turbine (Nedwell et al. 2007a; Edwards et al. 2007; Betke et al. 2004, see also Wahlberg and Westerberg 2005 and Madsen et al. 2006). The particle acceleration resulting from an operational wind turbine has also been measured by Sigray et al. (2011) with the resultant levels being considered too low to be of concern for behavioural reactions from fish. Furthermore, the particle acceleration levels measured at 10m from the turbine were comparable with hearing thresholds. Whilst limited, the available data provides an indicator that operational wind turbines are unlikely to result in disturbance of fish except within very close proximity of the turbine structure, as postulated by Wahlberg and Westerberg (2004). However, the available measurement data is mostly for smaller turbines (up to 1.5MW) and it may be expected that larger wind turbines could result in different acoustic characteristics, with foundation type also having an influence on the acoustic characteristics of the noise radiated from the structure (e.g. Marmo et al. 2013).
135. Noise would also result from surface vessels servicing the windfarm. However, noise levels reported by Malme et al. (1989) and Richardson et al. (1995) for large surface vessels indicate that physiological damage to marine fauna is unlikely, although the
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm Appendix 9.1 Underwater Noise Modelling 62
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150