Abstract
Monitoring ocean acoustic noise has been the subject of considerable recent study, motivated by the desire to assess the impact of anthropogenic noise on marine life. A combination of measuring ocean sound using an acoustic sensor network and modelling sources of sound and sound propagation has been proposed as an approach to estimating the acoustic noise map within a region of interest. However, strategies for developing a monitoring network are not well established. In this paper, considerations for designing a network are investigated using a simulated scenario based on the measurement of sound from ships in a shipping lane. Using models for the sources of the sound and for sound propagation, a noise map is calculated and measurements of the noise map by a sensor network within the region of interest are simulated. A compressive sensing algorithm, which exploits the sparsity of the representation of the noise map in terms of the sources, is used to estimate the locations and levels of the sources and thence the entire noise map within the region of interest. It is shown that although the spatial resolution to which the sound sources can be identified is generally limited, estimates of aggregated measures of the noise map can be obtained that are more reliable compared with those provided by other approaches.
Highlights
There has recently been increasing concern over the potential effects of anthropogenic acoustic noise on marine life, and the influence this noise poses for the sustainability of key marine species, biodiversity, ecosystems and the overall health of our seas [1,2,3]
Results for the measurement approach are not shown because the noise map is constant over the region of interest in this case. (In these graphs the ships do not appear as circles, which is a result of the difference in scales in the horizontal and vertical directions.) It is seen in the middle graph that there are parts of the region of interest, e.g., the vertical strip between grid points 100 and 200 in the horizontal direction, where the values of the acoustic noise map are underestimated, which correspond to ships that are missing because they are unknown
An approach has been described that uses measurements of ocean sound provided by a network of acoustic sensors, partial information about the locations and sound levels of the sources of the sound, and models of the acoustic output of the sources and for sound propagation in the ocean, to estimate the sound field produced by the sources anywhere within a region of interest
Summary
There has recently been increasing concern over the potential effects of anthropogenic acoustic noise on marine life, and the influence this noise poses for the sustainability of key marine species, biodiversity, ecosystems and the overall health of our seas [1,2,3]. The second step, sound prediction, uses the solution to the source reconstruction problem to provide estimates of the mean squared sound pressure, which is related to acoustic intensity, at any location within the region of interest In terms of these estimates, aggregated measures of the sound field, such as the spatially averaged sound pressure level, can be calculated. It is shown that the spatial resolution to which the source reconstruction problem can be solved is generally limited, reliable estimates of the spatially averaged sound pressure level can be obtained, and the approach can provide support to an implementation of the Marine Strategy Framework Directive.
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