A Numerical and Experimental Study on the Noise Absorption Behavior of Functionally Graded Materials Considering Geometrical and Material Influences

The investigations presented in this paper focus on insulation materials like foams and microfibers which will be used together as multilayer systems and mounted on vibrating surfaces to create a damping effect that reduces the radiated sound. The experiments and simulations are carried out on an aluminum plate and a steel sheet. The structure-borne noise is induced by a shaker. The results of the investigations provide generalized guidelines for optimizing damping material geometry and design according to the specifications of their application. In this contribution, the acoustical behavior of the damping materials will be examined and correlated with their geometrical and material properties. The investigated materials are microfibers and polyurethane foams that are mounted at the vibrating surface with a second layers as a mass layer. The mass layers are produced by a surface impregnation to different depths and with different densities or with plastic plates of a thickness of about 4.0 mm. The influence of the material thickness on the damping behavior is investigated as well as the influence of a thin foil adhered to the surface. The evaluation presented here considers the overall acoustic effect as well as different frequency ranges and their respective amplitudes.