Investigation of sound pressure waveforms helps the selection of appropriate metrics to evaluate their effects on marine life in relation to noise thresholds. As marine animals move farther away from a sound source, the temporal characteristics of sound pressure may be influenced by interactions with the sediment and the sea surface. Sound pressure kurtosis and root-mean-square (rms) sound pressure are quantitative characteristics that depend on the shape of a sound pulse, with kurtosis related to the qualitative characteristic “impulsiveness.” After verifying the propagation modeling approach using selected test cases from the JAM Workshop held in Cambridge, UK, in 2022, the time dispersion values of pressure signals produced by an individual airgun shot across various sediment types are analyzed. The results reveal that there is significant pulse dispersion when the seabed consists of predominantly sand-type sediments: i.e., the airgun signal duration increases considerably over long distances, thus decreasing the kurtosis of a sequence of pulses, whereas the pulse dispersion is more limited for clay and silt-type sediments. The range variations of frequency weighted kurtosis and rms sound pressure differ from those of the unweighted kurtosis, depending on the corresponding lower and upper roll-off frequencies corresponding to different marine animal groups.

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Anthropogenic sound in the marine environment can have negative consequences for marine fauna. Since most sound sources are intermittent or continuous, estimating how many individuals are exposed over time remains challenging, as this depends on the animals’ mobility. Here we explored how animal movement influences how many, and how often, animals are impacted by sound. In a dedicated study, we estimated how different movement strategies affect the number of individual harbour porpoises Phocoena phocoena receiving temporary or permanent hearing loss due to underwater detonations of recovered explosives (mostly WWII aerial bombs). Geo-statistical distribution models were fitted to data from 4 marine mammal aerial surveys and used to simulate the distribution and movement of porpoises. Based on derived dose–response thresholds for temporary (TTS) or permanent threshold shifts (PTS), we estimated the number of animals affected in a single year. When individuals were free-roaming, an estimated 1200 and 24000 unique individuals would suffer PTS and TTS, respectively. This equates to respectively 0.50 and 10% of the estimated North Sea population. In contrast, when porpoises remained in a local area, fewer animals would receive PTS and TTS (1100 [0.47%] and 15000 [6.5%], respectively), but more individuals would be subjected to repeated exposures. Because most anthropogenic sound-producing activities operate continuously or intermittently, snapshot distribution estimates alone tend to underestimate the number of individuals exposed, particularly for mobile species. Hence, an understanding of animal movement is needed to estimate the impact of underwater sound or other human disturbance.@en

The European Union requires member states to achieve or maintain good environmental status for their marine territorial waters and explicitly mentions potentially adverse effects of underwater sound. In this study, we focused on producing maps of underwater sound from various natural and anthropogenic origins in the Dutch North Sea. The source properties and sound propagation are simulated by mathematical methods. These maps could be used to assess and predict large-scale effects on behavior and distribution of underwater marine life and therefore become a valuable tool in assessing and managing the impact of underwater sound on marine life.@en