An Airgun Array Source Model Accounting for High-Frequency Sound Emissions During Firing—Solutions to the IAMW Source Test Cases

JASCO's Airgun Array Source Model (AASM) is a combined deterministic and stochastic model that separately treats the low-frequency and high-frequency components of signals produced by airgun arrays. The low-frequency module is based on solving the equations of motion for interacting spherical bubbles. The high-frequency module is based on a stochastic model of the airgun spectrum, which has been derived from a principal component regression analysis of the experimental data. This stochastic model determines the frequency spectrum of an airgun waveform during the rapid onset of a pressure that occurs when air is released from the gun chamber. AASM combines the output of these two modules to predict the source waveform of an airgun array over a wide frequency range (0-25 kHz). AASM was among the source models included in benchmark comparisons presented at the International Airgun Modeling Workshop (IAMW), held in Dublin, Ireland, in 2016. Results from the workshop showed that different source models agreed reasonably well at low frequencies (<;200 Hz), but they diverged substantially at high frequencies (>1 kHz). To help better understand the reasons for a mismatch between source models, this paper presents solutions to the IAMW source test cases, calculated using AASM, as well as a detailed description of AASM's theoretical underpinnings.