Directionality of Tonal Components of Ship Noise Using Arctic Hydrophone Array Elements

The horizontal directionality of ship-radiated noise was estimated in the Canadian Arctic Archipelago using two 48-element bottom-mounted hydrophone arrays. Source levels (SL) were estimated using automated identification system data for distance and bearing with a geometric spreading propagation loss model for ships passing within 3 km of the arrays. Time-averaged received levels are calculated in 3-s increments for broadband (10–600 Hz) as well as selected narrowband tonal sources. Tonal components are identified with spectral analysis and algorithmically tracked in the time-frequency domain. From the difference of received levels and propagation loss, SLs are calculated and sorted by ship's bearing from each of the 96 array elements for both broadband and predominant narrowband sources. Broadband SL estimates ranged from 148 to 181 dB re 1 μPa² m² for the four ships of opportunity.