Scattering and Absorption of Sound by a Compound Cylindrical Porous Absorber with an Eccentric Core

The classical method of separation of variables along with the novel features of Biot theory of dynamic poroelasticity and the translational addition theorem for cylindrical wave functions are employed to present an exact solution for interaction of a plane acoustic wave with a composite cylindrical sound absorber suspended in air. The analytical results are illustrated with numerical examples in which a compound cylindrical absorber made of selected configurations of two common sound absorbent materials (plastic foam and light glass wool), is insonified by plane sound waves at selected angles of incidence. The backscattered form function amplitude as well as the absorption cross section spectra are calculated and discussed for representative values of the parameters characterizing the system. The effects of incident wave frequency, angle of incidence, core eccentricity and coating thickness are examined. Limiting cases are considered and fair agreements with available solutions are obtained.