New paper on averaging shipping noise levels (Nathan Merchant)
Dear Colleagues, my co-authors and I are pleased to announce the publication of a paper examining methods of averaging shipping noise levels for environmental impact assessment. This work has particular relevance to policymakers concerned with long-term underwater noise trends and researchers investigating the effects of chronic noise exposure on marine life: Averaging underwater noise levels for environmental assessment of shipping Nathan D. Merchant, Philippe Blondel, D. Tom Dakin, and John Dorocicz, Journal of the Acoustical Society of America 132 (4), EL343-EL349 (2012), DOI:10.1121/1.4754429 Abstract Rising underwater noise levels from shipping have raised concerns regarding chronic impacts to marine fauna. However, there is a lack of consensus over how to average local shipping noise levels for environmental impact assessment. This paper addresses this issue using 110 days of continuous data recorded in the Strait of Georgia, Canada. Probability densities of ?10^7 1-s samples in selected 1/3 octave bands were approximately stationary across one-month subsamples. Median and mode levels varied with averaging time. Mean sound pressure levels averaged in linear space, though susceptible to strong bias from outliers, are most relevant to cumulative impact assessment metrics. This journal is open access and the paper can be downloaded free of charge here: http://link.aip.org/link/?JAS/132/EL343 Kind regards, Nathan Merchant PhD Researcher Department of Physics University of Bath BA2 7AY, UK +44 1225 385543 n.d.merchant@bath.ac.uk http://people.bath.ac.uk/ndm23/
Dear MARMAMers, those of you involved in passive acoustic monitoring may be interested in our recent paper on performance assessment of PAM devices and statistical characteristics of noise levels: Spectral probability density as a tool for ambient noise analysis Nathan D. Merchant, Tim R. Barton, Paul M. Thompson, Enrico Pirotta, D. Tom Dakin, and John Dorocicz, J. Acoust. Soc. Am. 133, EL262-EL267 (2013) Abstract This paper presents the empirical probability density of the power spectral density as a tool to assess the field performance of passive acoustic monitoring systems and the statistical distribution of underwater noise levels across the frequency spectrum. Using example datasets, it is shown that this method can reveal limitations such as persistent tonal components and insufficient dynamic range, which may be undetected by conventional techniques. The method is then combined with spectral averages and percentiles, which illustrates how the underlying noise level distributions influence these metrics. This combined approach is proposed as a standard, integrative presentation of ambient noise spectra. The paper is open-access and can be downloaded free here: http://dx.doi.org/10.1121/1.4794934 Kind regards, Nathan Merchant -- Nathan Merchant PhD Researcher Department of Physics University of Bath BA2 7AY, UK +44 1225 385543 n.d.merchant@bath.ac.uk http://people.bath.ac.uk/ndm23/
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Nathan D. Merchant -
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