A damping approach for enhancing low-frequency signatures from large-scale airgun bubbles

ABSTRACT As the demand for deep-sea resource exploration continues to grow, the optimization of low-frequency performance has become a critical objective in the design and control of marine airgun sources. A damping screen, installed at the outlet of a large-scale airgun, was investigated as a method to shift the dominant frequency of the acoustic signal toward lower frequencies. Based on a validated numerical model of compressible airgun bubble dynamics, a systematic analysis was conducted to assess the impact of the damping screen’s geometric dimensions on bubble dynamic characteristics, the airgun’s pressure wavelet, and its sound pressure level spectrum. The damping screen effectively regulated the airgun’s performance by actively intervening in and reshaping the dynamic behavior of the bubble. A principal finding was that the damping screen successfully lowered the dominant frequency of the airgun, revealing a predictable, regulatory relationship between the screen’s dimensions and the source’s dominant frequency. Furthermore, the influence patterns of the damping screen’s dimensions on other key performance indicators, including the characteristics of the primary pulse, as well as the strength and period of the bubble pulse, were determined. A damping screen, therefore, shows promise as a novel approach for achieving targeted modulation of the dominant frequency in airgun source signatures.