ACOUSTIC SCATTERING FROM SWIM-BLADDER FISH AT LOW-FREQUENCIES

Models of acoustic resonant scattering from swim-bladder fish are sens itive to the choice of damping coefficient and resonance frequency. Ex isting theory does not provide a consistent representation of the role played by tissue surrounding the swim bladder in determining this coe fficient and empirical fits are therefore often used to adjust model p arameters for specific examples. In an attempt to provide a firmer the oretical basis for the interpretation of experimental results, it is s hown how the elastic properties of the tissue can be combined with the swim bladder in a consistent way. Although the analysis must eventual ly be extended to swim bladders of arbitrary shape, for simplicity the essential features are illustrated with a spherical geometry. The res ults emphasize the need for accurate measurement of the bulk elastic p roperties of tissue, specifically the complex shear modulus.