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/