Bailey, H., Parvin, S., Senior, B., Simmons, D., Rusin, J., Picken, G. & Thompson, P.M. (2010) Assessing underwater noise levels during pile-driving at an offshore windfarm and its potential effects on marine mammals. Marine Pollution Bulletin 60: 888-897.
Marine renewable developments have raised concerns over the impact of underwater noise on marine species, particularly from pile-driving. Environmental assessments typically use generic sound propagation models to assess potential impacts, but empirical tests of these models are lacking. As part of the Beatrice demonstration project, we measured pile-driving noise associated with the installation of the jacket sub-structures for the two 5 MW wind turbines that were installed in deep water off NE Scotland.
Helen Bailey's Marine Pollution Bulletin paper presents simultaneous calibrated recordings made close to the development site (100m from the piling operation) and at a series of different distances up to 80km from the site. At 100m, the maximum peak-to-peak sound level was 205 dB re 1 lPa, gradually reducing to background levels 80km away from the site. These measurements indicted that pile-driving noises could be detected by dolphins at ranges of up to 70 km. Comparison of these measured data with predictions from propagation models suggest that the models provide a reasonable estimate of received levels. But evaluation of these data in relation to published noise exposure criteria highlighted the uncertainty over how different marine mammal species might react to these received noise levels. This work has now led to further large-scale studies of behavioural reactions to anthropogenic noise that we are carrying out for DECC.