Inter-pulse sound field from a marine seismic survey in the Arctic and its potential effects on marine mammal acoustic masking

Abstract

It has been documented that reverberant fields from marine seismic surveys elevate sound levels, and thus has the potential to mask acoustic signals that are important to marine mammals. In this study, we investigated one-third-octave (OTO) bands of airgun inter-pulse sound fields from a shallow water (<15 m) seismic survey in the Beaufort Sea. The results show that at close distances less than 3 km, peak energy of the OTO band levels were concentrated around 80-110 Hz and the median sound levels were 40-50 dB above ambient. The higher frequency components (>3 kHz) of inter-pulse sound field at these close distances ranged 5-20 dB above ambient. At distances beyond 3 km, the received acoustic energy becomes more uniform up to 1000 Hz. The median OTO band levels at these distances were approximately 10-20 dB above ambient. For higher frequencies, sound levels at these distances were approximately the same as ambient. These results imply that low-frequency bowhead whales could be affected by acoustic masking from seismic airgun inter-pulse sound fields, especially at relatively close distances. However, potential acoustic masking effects to mid-frequency beluga whale echolocation signals are expected to be less profound.