Economic globalization and the continuous search for food, energy and raw materials led to an estimated 3 dB/decade increase of ocean noise intensity. Determining the level of anthropogenic noise, the so-called excess noise, and building identifiable meaningful indicators for supporting marine management policies currently requires extensive observation data and computer modeling. For modeling purposes, in this study, anthropogenic noise was reduced to shipping traffic drawn from Automatic Identification System data, and environmental sound was attributed to surface wind only. Data-model comparison allowed introducing a methodology for simple model calibration and estimate excess noise. This methodology was tested on acoustic recordings performed in June 2018 at three locations to the southwest of Faial-Pico Islands in the Azores archipelago. The results show that field-calibrated excess noise sound maps are in line with the shipping distribution in the area, revealing a number of potentially marine life-threatening hotspots. Excess noise addresses the need for a quantifiable measure of ocean noise only and therefore offers a basis for building suitable continuous anthropogenic noise pollution indicators.

The Azores archipelago is an important cetacean habitat spot, registering a very relevant resident and migratory population. Due to its geographical position, it also represents an important commercial crossroad between America and Europe. Vessels represent the major source of underwater noise which may affect cetaceans. Since 2017 acoustic measurements have been performed in the southern side of the channel between Pico-Faial. Although foreground biological signatures are numerous and relatively easy to spot in the data, it is not clear how to separate background abiotic, biotic and man made noise and, therefore, to single out the noise due to shipping. In order to address these questions, a shipping noise prediction tool using a 10-min resolution AIS coverage of the area, together with bathymetric, water column space-time descriptors and surface wind generated noise model, showed a significant noise variability between Pico-Faial islands. This variability was mainly observed in the strait and to the south of it, both along the coast associated with ferries and around offshore banks due to fishing activity. Time series of predicted sound pressure level at three receiver locations favorably compare with it in-situ noise measurements in the 44-177Hz a frequency band.