| Summary: | Functional marine mammal acoustic communication evolved under natural ambient noise levels, which makes communication vulnerable to intense, anthropogenic noise sources. We consider the potential long-range reduction effects of airgun noise on marine mammal communication range. During the propagation process, airgun impulses are reflected multiple times from the sea surface, refracted in sound channels, and reverberate leading to signal stretching that may result in a continuous received sound. We conducted sound propagation modelling using AcTUP (Acoustic Toolbox User-interface & Postprocessor) to estimate propagation loss and model the received seismic impulse waveform at 100, 500, 1000 and 2000 km distance from the source, and at 10, 50 and 200 m receiver depth for shallow (500 m) and deep sea (4500 m) Antarctic conditions. Modelled waveforms were overlaid with marine mammal vocalizations (song of fin whale Balaenoptera physalus and blue whale Balaenoptera musculus intermedia and Weddell seal Leptonychotes weddelli vocalizations) to assess the distances over which communication masking could occur. Signals were analysed using a leaky integrator and peak detector model within the bandwidth of the modelled vocalization. Hearing abilities of baleen whales were assumed to be noise limited at sea state 4. Preliminary results indicate that airgun noise is intermittent up to 1000 km from the source, changing to a continuous noise between 1000 and 2000 km. Results of masking modelling indicate that airgun sounds can lead to a reduction in communication range for blue and fin whales 2000 km from the source depending strongly on the frequency content of the vocalization.
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