Inter-pulse noise field during an Arctic shallow-water seismic survey

Abstract

Marine seismic surveys using airgun arrays generate intense underwater acoustic pulses. Those pulses may cause hearing impairment and/or behavioral disturbances in marine mammals. Few studies have investigated the resulting multipath propagation and reverberation from these pulses. This research uses acoustic recordings collected in a shallow region of the Beaufort Sea during an open-water seismic survey to characterize the noise field between airgun pulses. The disturbances between pulses are collectively referred to as the inter-pulse sound. Two methods were used to quantify the inter-pulse sound: the incremental computation method and the Hilbert transform method. The incremental computation method calculates the root-mean-squared sound pressure level in various sub-intervals, and the Hilbert transform method is used to calculate instantaneous acoustic amplitudes. Analyses using both methods yield identical results, showing that the inter-pulse sound field exceeds ambient noise levels by as much as 9 dB during relatively quiet conditions. The results also indicate that inter-pulse noise levels are related to the source distance. These two methods can be used to quantify the impact of anthropogenic transient noises on the acoustic environment and to address acoustic masking in marine mammals.