Development of a system for monitoring and assessment of underwater sound

The Bulgarian Black Sea coast is an area with intense human activity, but also there is a complex ecosystem. Several anthropogenic sources generate loud sound levels in this area. The two most wide spread are maritime transport and hydrocarbon exploration and exploitation in the Bulgarian offshore sector. Underwater sound may have negative impact on animals in the Bulgarian waters that are sensitive to sound, such as marine mammals and certain fish species. 

The knowledge of ambient noise levels is very important for the characterization of the environmental status with regard to the European Marine Strategy Framework Directive (MSFD). The directive is aiming at a more effective protection of the marine environment including the protection of marine life exposed to noise, and the improvement of the health of the marine environment as a whole.

To estimate this impact the ocean technologies department of Bulgarian Institute of Oceanology developed a system to monitor the sound generated by marine activities following the TSG Noise guidance. The aim was to provide an integrated solution to monitor and asses the noise impact of ship traffic or other marine activities. The development was funded by program BG02 "Integrated management of marine and inland waters" financed by the financial mechanism of the European economic Area (EEA FM) 2009-2014.

The system consists of monitoring and simulation components. The combination of numerical modelling and noise measurements at selected locations offers a credible solution to the problem of underwater noise monitoring. The monitoring component comprises an array of passive sound recorders, equipped with hydrophones, self-contained power supplies, data acquisition and storage electronics. The simulation tool is in development. Suitable modelling approaches, modelling scenarios, and acoustic model input values are being selected and applied for the most important sources of sound and for underwater sound propagation in the Bulgarian waters. The tool computes sound maps produced by multiple noise point sources, as input for assessment of the environmental status. For optimum results, the simulation tool will be validated using acoustic measurements provided by the monitoring tool.

Future work includes development of a post-processing tool of the sound maps to obtain indicators relevant to both the noise anthropogenic pressure and biological effect of underwater noise impact on marine life.