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The impact of man-made underwater noise on the marine environment has recently received increased attention from regulatory authorities, as evidenced by inclusion in the Marine Strategy Framework Directive (MSFD). Radiated underwater noise from ships, primarily resulting from propeller cavitation, has for many years been understood to be one of the major contributors to ambient ocean noise. Civilian research in this area has to date been relatively limited; standards covering the measurement of radiated noise from ships in deep water and associated data analysis procedures have only recently been published by national and international standards institutes. Less attention has so far been paid to the measurement of radiated noise from ships in shallow water environments. This is of interest as shallow water areas are more likely to be used by civilian researchers due to the logistical problems involved in undertaking trials in deep water. The issue of shipping noise has been identified as one requiring further research, indicated by the recent funding of several large collaborative projects by the EU (e.g. the SILENV, AQUO and SONIC projects). This paper presents ship radiated noise data measured using a three hydrophone array during a sea trial undertaken as part of the SONIC project.

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The increased interest in the potential environmental impact of noise from shipping is resulting in the development of measurement methods for determining the radiated noise level and equivalent monopole source level of vessels. It is important to understand the random and systematic uncertainties associated with such techniques. The EU SONIC project provided an opportunity to make repeated measurements on the University of Newcastle research vessel, the Princess Royal, in a shallow water environment (100 m deep) over a number of days. Two multiple hydrophone arrays operated by two of the project partners, CETENA and the University of Southampton, were deployed from the same moored support vessel. This data is reviewed to illustrate the variation associated with such measurements and the impact of using multiple hydrophones and multiple measurement runs on the uncertainty in the radiated noise level and the calculated source level. The results are also compared with a later measurements of the same vessel in a different shallow water environment (20 m deep) using bottom moored hydrophones.

The potential impact of man-made underwater noise on the marine environment is receiving increased attention. Shipping is one of the main sources of such anthropogenic noise. In order to understand the underwater soundscape considerable effort is being placed on generating underwater noise maps, based on using AIS data to provide details of vessel locations and operational characteristics. A key input for noise mapping models is an adequate knowledge of the source strength and characteristics for each vessel. Currently the sources are usually assumed omnidirectional, given the limited data on the true vessel radiation pattern. As part of the EU SONIC (Suppression of underwater Noise Induced by Cavitation) project measurements were undertaken on a small survey vessel, operating under realistic conditions at sea in shallow water. An autonomous recorder was used to measure the sound pressure as a function of range and azimuth. The vessel made a repeated runs past the autonomous recorder for a variety of different ranges. This has enabled the vessel noise footprint to be measured as a function of frequency and speed for the vessel, showing how the azimuthal characteristics change with frequency.