Measurement of particle motion from an offshore piling event in the North was conducted to determine noise levels. For this purpose, a bespoken sensor was developed that was both autonomous and sensitive up to 2 kHz. The measurement was undertaken both for unmitigated and mitigated piling. Three different types of mitigation techniques were employed. The acceleration zero-to-peak values and the acceleration exposure levels were determined. The results show that inferred mitigation techniques reduce the levels significantly as well as decreases the power content of higher frequencies. These results suggest that mitigation has an effect and will reduce the effect ranges of impact on marine species.

The project entitled “UNderwater Acoustic Calibration standards for frequencies beLOW 1 kHz” (“UNAC-LOW”), currently active within the European Metrology Programme for Innovation and Research (EMPIR), is presented by describing its objectives and current activities. The project aims at developing the metrological capacity of the European Union (EU) for the calibration of hydrophones and autonomous recording systems for the frequency range between 20 Hz and 1 kHz, for which traceability is presently not fully available. In this way, EU metrological capacities for absolute measurement of underwater sound will be improved, with a direct effect on the implementation of regulation and EU Directives that require underwater acoustic measurements to be traceable. After having completed the initial project tasks regarding the review of existing methods and the design of the experimental setups, comparison measurements between the project partners are currently under way and their results will be validated and presented upon project end after first quarter of 2019. To ensure long-term operation of the calibration capabilities by each partner, a coherent EU metrology strategy for underwater acoustics will be developed as one of the main project outcomes. Current activities include the implementation of the calibration setups developed in earlier stages of the project for both hydrophones and autonomous recorders. The methods that shall be used for hydrophones are the pressure method in a closed chamber and the standing wave tube method. For autonomous recorders, in addition to the above methods, calibrations will be performed using free-field methods in different open-water test sites possessing suitable characteristics for low frequency measurements.

The Marine Strategy Framework Directive (MSFD) has been an important driver for progress in monitoring and assessment of impulsive underwater noise in the marine environment of the European Union. An important achievement of the MSFD implementation was the development of regional noise registries, providing the data basis for assessments. Recently, the EU has made tremendous efforts to propose harmonized assessment approaches and first-of-their-kind regional quantitative thresholds for impulsive underwater noise. In light of these newly developed thresholds values, we analyze the suitability of the available data in the noise registries for assessment purposes under the MSFD and review sources of uncertainties regarding quantitative results. We present three regional case studies located in the North Sea, the Baltic Sea and the Mediterranean Sea. For each of these regions, a sound-intensive activity was selected that aligned with a realistic impulsive noise event reported for the region. We made use of available data in the noise registries and applied the EU Guidance recommended for the description of impulsive noise sources, but also used alternative approaches and observations as comparison. The case study analysis includes the evaluation of data availability, data quality and data accuracy in the noise registries, and identifies corresponding consequences of the data for the uncertainty and interpretability of assessment results, especially for the quantitative evaluation of habitat areas impacted by noise. Finally, we make suggestions for the improvement of the data basis in the noise registries and the optimization of the assessment accuracy.

In this study, we present the first iteration of DPower, an energy conserving method for use in underwater acoustic networks. The method encompasses a straightforward transmission power calibration procedure and adaptive power level selection. The method was evaluated in combination with DFlood, a known and validated constrained flooding protocol developed for underwater applications. Simulations of a network with given prerequisites have shown that, with an acceptable increase in packet loss, the presented method can dramatically reduce the energy consumption and thus improve the life-time of networks.