Pure elastic resonance scattering for submerged elastic objects with separable geometries

I.IntroductionTheResonanceScatteringTheory(RST)wasdevelopedasabasicmethodtoanalyzesoundscatteringfromelasticobjectsimmersedinwater.Itwasusedtocylindricalandspher-icalgeometries,includingsolidandshellobjects.TheRSTinvestigatesmainlytheresonancespectrumofscatteredwavefromanelasticobjectexcitedbytheincidentwave.Theresonallcespectrum,namedthe'AcousticSpectroscoPy',reflectsmaterialcharactersoftheobjectsandcanbeusedtoidentifythetarget.Theresonallcespectraareisolatedbysubtractingfromthescattere…

Pure elastic resonance scattering for submerged elastic objects with separable geometries

Theoretically, the extraction of resonance scattering spectra is performed by a pure elastic scattering function, which is defined as the total scattering function subtracts an appropriate background term. In this paper, we derive a simple and explicit expression of the pure elastic scattering function for the separable geometries immersed in water. It depends on the modal mechanical impedance and acoustic impedance except a phase factor only relative to the geometry Analyses used the new expression leads to two Kinds of resonances with distinguishable character: the elastic-borne wave resonances and the fluid-borne wave resonances. The former depends mainly on elasticity of the object and the fiuid-loading has secondary effect. The later is related closely with the liquid-loading and vanishes if the liquidloading vanishes. This allows us to classify the family of individual resonance correctly. Taking into account the contributions of the fluid-borne wave resonances, we modify the conventional resonance scattering formula by use of the Singularity Expansion Method.