Sound radiation of orthogonally rib-stiffened sandwich structures with cavity absorption

A comprehensive theoretical model is developed for the radiation of sound from an infinite orthogonally rib-stiffened sandwich structure filled with fibrous sound absorptive material in the partitioned cavity, when excited by a time-harmonic point force. The vibrations of the rib-stiffeners are accounted for by considering all possible motions. Built upon the concepts of dynamic density and bulk modulus, both frequency dependent, an equivalent fluid model is employed to characterize the absorption of sound in the fibrous material. Given the periodicity of the sandwich structure, Fourier transform technique is employed to solve the series of panel vibration equations and acoustic equations. In the absence of fibrous sound absorptive material, the model can be favorably degraded to the case of an infinite rib-stiffened structure with air or vacuum cavity. Validation of the model is performed by comparing the present model predictions with previously published data, excellent agreements are achieved. The influences of air–structure coupling effect and cavity-filling fibrous material on the sound radiation are systematically examined. The physical features associated with sound penetration across these sandwich structures are interpreted by considering the combined effects of fiberglass stiffness and damping, the balance of which is significantly affected by stiffener separation. The proposed model provides a convenient and efficient tool for the factual engineering design of this kind of sandwich structures.