Insights into the Calculation of Metrics for Transient Sounds in Shallow Water

Concern about possible impact of human activity on marine life has led to regulation in the USA [1,2] and the EU [3].The EU’s Marine Strategy Framework Directive [3] requires member states to achieve Good Environmental Status (GES) by 2020. Descriptor 11 of GES is “Introduction of energy, including underwater noise, is at levels that do not adversely affect the marine environment”, for which two indicators are specified [4]. The effect of underwater sound on aquatic animals is a research topic in need of multidisciplinary effort between acousticians and biologists, in order to provide a quantitative description of the sound field and to understand the impact of the sound on aquatic life. Sound exposure level (SEL), sound pressure level (SPL) and peak pressure are widely used as metrics for assessing environmental impact [5, 6].This paper described the calculation of SEL and SPL for impulsive sounds in shallow water (relevant to Indicator 11.2.1 of GES Descriptor 11), with particular attention to the difficulties ass