The CMST Airgun Array Model—A Simple Approach to Modeling the Underwater Sound Output From Seismic Airgun Arrays

This paper describes the theoretical and numerical basis for the Centre for Marine Science and Technology airgun array model (Cagam), a relatively simple airgun array model that has been used by the center for a number of years. Comparisons with the measured data from the International Association of Oil and Gas Producers Exploration and Production Sound and Marine Life, Joint Industry Programme Svein Vaage Broadband Airgun Study data set, were carried out for a single airgun of a range of sizes and types and several two-gun clusters. When calibrated for the time integrated squared pressure, the model predicted positive peak levels to an accuracy of ±0.6 dB and successfully predicted the overall spectral shape, including its high-frequency roll-off. There were larger errors in prediction of negative peak pressures, with Cagam underpredicting the negative peak pressure by up to 2.3 dB. For a single airgun, Cagam tended to slightly overestimate the bubble pulse frequency and to underestimate the bubble damping, with both these discrepancies increasing for two-gun clusters. A comparison with the Agora2 model, used for several studies by participants in the 2016 International Airgun Modelling Workshop, is also included.