Computing cumulative sound exposure levels from anthropogenic sources in large data sets

Abstract

The goal of many underwater acoustic environmental assessments is to characterize the soundscape in an area before, during or after an anthropogenic activity. The assessment determines the range of baseline noise levels from natural and anthropogenic sources and the contribution of the new anthropogenic activity. The noise levels are considered in aggregate for possible effects on the environment. It is accepted that the effects of anthropogenic noise on marine life depend on the intensity and duration of exposure, the frequency content of the sound relative to the hearing abilities of the species, and the behaviour context of the species exposed to the sounds. A growing body of scientific evidence is being analyzed to establish threshold sound levels and dose-response curves for injury or behavioural disturbance effects to marine life. Recent research is also raising new questions about the most appropriate ways to compute ambient sound levels and exposure metrics. In this paper we present our methods for quantifying ambient sound levels and anthropogenic sound levels from shipping and seismic survey activities in large data sets. We also make recommendations on how to estimate background sound levels in the presence of these sound sources. © 2013 Acoustical Society of America.