During the exploration, development, production and decommissioning phases of offshore oil and gas reserves these activities contribute to the noise levels in the oceans, estuaries and rivers of the world. The purpose of this report is to catalogue and assess the available data that characterise the underwater sounds made by the oil and gas industries in all phases of their activities. Measurements of underwater sounds are scarce. Given the volume of traffic and industrial activity in, on or by the shores of the oceans it is surprising that so little is known of the likely impact man made noise may have within the oceans. Measurements made over the last 40 years at a site off the southern Californian coast show a general increase in low frequency noise in the ocean with time. The increase in this noise level has been widely attributed to increases in shipping and other anthropogenous (human made) noise (this is often termed anthropogenic noise). The significant amount of shipping and other activities attributable to oil and gas industries contributes to this rise in the total background noise in the ocean. In some areas, ocean noise background levels have doubled every decade for the last six decades mainly due to the increase in shipping. (McDonald, Hilderbrand et al. 2006). Few measurements have been made on underwater noise sources, and those that have been made are often limited in their scope due to vessel time, operational and weather constraints. Comparison between measurements by different observers can be difficult due to the vast range of ever changing conditions encountered in the ocean seabed, and sea-surface. Many metrics can be used to describe the acoustic properties of a sound source with little standardization between experiments. Local conditions (geographic, geological, oceanographic and meteorological) all have a very substantial impact on the way in which sound propagates from a source through the water to a measurement receiver. As the receiver is often a considerable distance from the source it is usually necessary to measure many other parameters in order to attempt to determine the true nature of the source itself. This report reviews the available data on noise in the oceans produced by the oil and gas industries however; due to the scarcity of data in some areas other noise sources are included in some sections for comparative purposes. The noise levels are presented as the measured values by the researcher and then in an extrapolated form in a consistent set of units. To do this extrapolation a number of assumptions have been made particularly relating to the local conditions under which the measurements were determined and the nature of the source signal. The extrapolated values should be used as guidelines only as the variability of the transmission of sound and the nature of the sound source itself cannot enable an accurate translation between the remotely measured values and the extrapolated (back projected) values.
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