Verification of airgun sound field models for environmental impact assessment

The potential impact of seismic surveys on marine life has given regulators and scientists a shared interest in quantifying the sound field radiated by airgun arrays. Predictions do not always agree well with measurements, and there is a need to build confidence in model accuracy. To address this need, experts in airgun sound field modeling were invited to participate in an international workshop that took place in Dublin on 16 July 2016.The purpose of the Dublin workshop was to improve insight in the characterization of the airgun array sound field, including the interaction between source and propagation models. Well-specified, biologically relevant scenarios were developed, solutions were compared and the differences quantified. Possible causes of these differences were discussed. Qualitative agreement was demonstrated in the time domain source signature. In the frequency domain, inter-model differences exceeded 30 dB above 1 kHz. Differences in initial rise time were identified as the probable cause of these high frequency spectral differences. Observed differences in modeled far field sound levels are largely attributed to these differences in the source signature. Validation of the source models is identified as a priority.