Abstract
All sound comprises fluctuations in pressure and particle motion (PM) and all fishes and many aquatic invertebrates detect PM. Noise is unwanted or harmful sound, and underwater anthropogenic noise is a global pollutant. Therefore, a large proportion of marine life is potentially threatened by PM created by anthropogenic activity. There is building evidence that anthropogenic noise is detrimental to the health and survival of fishes and aquatic invertebrates, but the importance of PM to these effects remains unclear because until recently very few PM measurements have been taken, with studies mainly relying on sound pressure measurements to estimate PM exposure levels. In theory, PM cannot be predicted effectively from sound pressure in certain physical conditions. These physical conditions tend to be near the surface and the bottom, or in shallow water such as near shore, in lakes and rivers etc., where most aquatic life is found. Thus, there is a need to measure PM to establish the levels at which aquatic life can detect sound, levels at which adverse effects from anthropogenic activity occur, and to establish the boundaries for the physical conditions where sound pressure can or cannot be used to predict PM. PM sensors are becoming commercially available, while some scientists are also making their own, leading to an increase in the number of scientists taking PM measurements around the world. There is a need for guidance that helps scientists to understand what PM is and when it needs to be measured, how to select and calibrate instruments for such measurements, how to properly take measurements and then how to process and report the data for consistency and comparability between studies.
Our solution is this ‘Best Practice Guide’, with the following providing an outline of our key findings on best practice for PM measurement for biological applications.