Impedance of pistons on a two-layer medium in a planar infinite rigid baffle.
An integral transform technique is used to develop a general solution for the impedance of rigid pistons acting on a two-layer medium. The medium consists of a semi-infinite acoustic fluid on a viscoelastic thick plate in a rigid infinite baffle. The stresses acting on the planar baffle, as a result of piston motion, are determined using theory of linear elasticity and are therefore unrestricted in terms of applicable frequency range. The special case of a circular piston is considered and expressions for the self-and mutual impedances are developed and evaluated numerically. Numerical results are compared with classical piston impedance functions and finite-element model results. At low frequencies (k(0)a<1), the self-impedances vary significantly from the classical piston impedance functions due to the shear properties of the viscoelastic medium. In the midfrequency range (1<k(0)a<pi) the self-impedances vary from the classical piston impedance functions for moderate viscoelastic layer thicknesses (0.5<ha<2). The mutual impedances associated with pistons on a two-layer medium generally exhibit an increased decay, as a function of separation distance, over the classical results.
Hassan
Scott E
SE
NAVSEA Newport, Newport, Rhode Island 02841-5047, USA. hassanse@npt.nuwc.navy.mil
D000162:Acoustics / Q000295:instrumentation; D004548:Elasticity; D017097:Electric Impedance; D004867:Equipment Design; D020342:Finite Element Analysis; D005583:Fourier Analysis; D016014:Linear Models; D008962:Models, Theoretical; D009038:Motion; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D014783:Viscosity