From 1986 to 1989 a series of cruises were conducted in the central Mediterranean Sea, to determine distribution and relative abundance of cetaceans. Observation sessions lasted for a total of 2433 h. The presence of animals was assessed visually. Relative sighting frequencies among species and among subdivisions of the study area were calculated, based on observation time. Seven species were observed, including, in order of decreasing frequency: bottlenose dolphins (Tursiops truncatus), striped dolphins (Stenella coeruleoalba), fin whales (Balaenoptera physalus), sperm whales (Physeter catodon), Risso's dolphins (Grampus griseus), common dolphins (Delphinus delphis) and long-finned pilot whales (Globicephala melas). The highest sighting frequencies occurred in the Ligurian-Corsican Sea; cetaceans were scarcest in the Tyrrhenian Sea and in the northern Adriatic Sea. Bottlenose dolphins were found throughout the study area in neritic waters. Fin whales, sperm whales, Risso's dolphins, and striped dolphins were sighted in the offshore waters of the Ligurian-Corsican, Tyrrhenian, and Ionian Seas. The now rare common dolphin was mostly seen in the Sardinian Sea, in the Sicily Channel, and in the Ionian Sea. Pilot whales were observed, occasionally, in the Ligurian-Corsican and Tyrrhenian Seas.

The European Marine Strategy Framework Directive requires European member states to develop strategies for their marine waters leading to programs of measures that achieve or maintain good environmental status (GES) in all European seas by 2020. An essential step toward reaching GES is the establishment of monitoring programs, enabling the state of marine waters to be assessed on a regular basis. A register for impulsive noise-generating activities would enable assessment of their cumulative impacts on wide temporal and spatial scales; monitoring of ambient noise would provide essential insight into current levels and any trend in European waters.

The World Organization of Dredging Associations (WODA) has identified underwater sound as an environmental issue that needs further consideration. A WODA Expert Group on Underwater Sound (WEGUS) prepared a guidance paper in 2013 on dredging sound, including a summary of potential impacts on aquatic biota and advice on underwater sound monitoring procedures. The paper follows a risk-based approach and provides guidance for standardization of acoustic terminology and methods for data collection and analysis. Furthermore, the literature on dredging-related sounds and the effects of dredging sounds on marine life is surveyed and guidance on the management of dredging-related sound risks is provided.

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.