Coupling of wave data and underwater acoustic measurements in a maritime high traffic coastal area: a case study in the Strait of Sicily.

Underwater acoustic monitoring combined with real-time sea surface observations and numerical model forecasts could improve the efficiency of natural and anthropogenic sound source discrimination. In this work, acoustic sound pressure levels at different frequencies were compared with significant wave heights, measured using an X-band radar system, and then matched against independent data derived from a SWAN model in order to confirm their reliability. The acoustic data were recorded from a fixed buoy located in the Sicilian Channel at 4.9 km from the coast and 33 km from the X band radar system installed at Cape San Marco (in the south-west region of Sicily). All data were acquired during two different periods: from February 28th to March 16th 2015 and from April 23rd to May 27th 2015. The level of noise at the 16 Hz octave band showed the best linear correlation (R = 0.78), with in situ radar observations of significant wave height. Radar measurements of wave height coupled with in situ acoustic measurements give a characterization of the level of noise due to sea state in a specific area. These measurements could be used to discriminate natural sources of noise (waves) from other sound sources such as biological and anthropogenic sources. This discrimination contributes to understand the impact of acoustic pollution on marine environments and provides a monitoring plan protocol for safeguarding biodiversity in the Mediterranean coastal areas.