Cumulative noise exposure assessment for marine using sound exposure level as a metric

Sound exposure level (SEL) has been suggested as an important parameter when considering the impact of anthropogenic noise on marine mammals (Southall et al, 2007). This metric allows the cumulative exposure of an animal to a sound field for an extended period to be assessed against a predefined threshold for injury criteria. In many cases, this can become the dominant mechanism by which a marine mammal may suffer injury. In this paper, the SEL metric has been used to estimate the cumulative exposure of animals using two examples of sound sources: (i) an offshore Floating Production Storage and Offloading (FPSO) platform used in the oil and gas industry; and (ii) marine piling for offshore windfarm construction. The method has been used in a predictive manner using models for noise sources, and also using measured data of the noise radiated by the source. The method can be used to investigate the effect on the cumulative exposure of factors such as source level and transmission loss model. In addition, assumptions made about the behaviour of the animals have been assessed. Examples are provided of exposure estimates made for a static animal, a fleeing animal, or an animal in transit through the source region.