Frequency responses analysis of buried targets under subcritical incidence in bistatic sonar

Detecting buried man-made targets in the seabed from long distances using bistatic sonar is a challenging task. At long detection ranges, acoustic waves are incident on the seabed at subcritical angles, generating evanescent waves that propagate along the seabed. When evanescent waves are incident on a buried target located near the seabed interface, the elastic waves from the target radiated into the water column become complex. This study aims to investigate how the scattered waves from a buried elastic spherical shell vary with the receiver position under active bistatic sonar conditions, and to explore the potential of this phenomenon for detection. Finite element simulations and water tank experiments revealed that the elastic wave frequency of the buried spherical shell target increases in the forward scattering direction. [Work supported by KRIT grant funded by the Korea government(DAPA) (KRIT-CT-23-035, Study on low-frequency SAS platform motion estimation & correction and buried mine detection (‘24-’28)).]