Underwater sound and the potential impacts on marine life has received increased attention in recent years, with measures to assess underwater sound having been included within the European Marine Strategy Framework Directive (MSFD). As part of the proposed requirements of this Directive Member States may have to report on the occurrence and distribution of activities within their jurisdictions that generate loud, low and mid frequency impulsive sounds that exceed levels capable of causing significant impact to marine animals. However, current EC guidance does not provide any specific levels of sound that are deemed capable of causing a ‘significant impact’ to marine animals, so there remains considerable flexibility in how this can be interpreted by Member States. This report examines information on underwater sound generated by the offshore oil and gas industry, and reviews the main activities, these being: geophysical surveys, use of explosives, construction of oil and gas infrastructure, impact piling, production, vessel and drilling noise. The Department of Energy and Climate Change (DECC) is responsible for regulating the activities of the UK oil and gas industry and ensuring compliance with applicable legislation and European Directives. In order to provide DECC with an indication of what oil and gas activities could be considered as requiring reporting under new the Marine Strategy Framework Directive, a number of recognised sound exposure thresholds and pressure level indicators proposed by Southall et al (2007) and a specialist EU Task Group were compared against the sound levels generated by oil and gas activities. In the absence of any clear guidance as to the peak sound and exposure levels that are considered capable of causing significant impact to marine life, it was decided by the authors of this report that oil and gas activities that produced sound in excess of the levels deemed capable of inducing a Temporary Threshold Shift (TTS) in hearing of cetaceans using the Southall impact exposure criteria, were likely to qualify for reporting requirements. This assessment identified the following activities as being most likely for reporting: high powered sparker systems, high powered Boomers, single airguns in excess of 100 cubic inches, Airgun arrays, pile driving activities and use of explosives. The noise descriptor as specified in the MSFD is for low and mid frequency impulsive sounds within the frequency range of 10 Hz – 10 kHz. A number of oil and gas activities, whose sound levels were documented in this review, do not qualify under this criteria because they either produce continuous sounds (shipping and dredging) or generate high frequency sounds in excess of the upper limit of the noise descriptor (multibeam and side scan sonar). A difficulty faced when compiling information on underwater sound measurements is that much of the information presented in technical reports have not been subject to the rigours of the scientific review process. The accuracy of the data in many of the reports reviewed was difficult to ascertain due to lack of detail provided as to how measurements were recorded and the calibration methods applied to the recording equipment. This report provides a comprehensive review of sound pressure levels that are available for oil and gas activities and details the processes used by DECC to record information on activities most likely to be reported. This report will enable DECC to determine if any changes are required to the reporting of oil and gas activities and, should further guidance be provided on the sound levels that need to be reported, this will enable them to revaluate the oil and gas activities that have been preliminary identified within this report.

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