Study Of Sound Absorption Properties Of Metal Foam With Gradient Porosity

Metal foam is a porous structure with air pores and metal skeleton. It not only remains the characteristics of metal materials, but also has the characteristics of porous materials. In the field of noise control, metal foam has received much attention as a new kind of multi-function absorption material. Whereas these are still no further researches on the absorption abilities of metal foam with nonuniform porosity in the domestic and foreign. Therefore, this paper proposes a metal foam structure with gradient porosities,and the sound absorption properties of this structure have been studied in theoretical and simulate ways. The main work and achievements of this paper are as follows.This paper proposes a metal foam structure with gradient porosities, and uses Johnson-Champoux-Allard(JCA)model to simulate the sound absorption properties of metal foam with single-stage and double-stage gradient porosities structure. The sound absorption performances of the structures are studied by changing the gradient parameters.This paper puts forward an idea that the target frequencies can be absorbed precisely by changing the gradient parameters. The simulations demonstrate that the position of sound absorption peaks can be controlled accurately in the wide frequency range of metal foam with single-stage gradient porosities. A 3D diagram with the relationship between the gradient porosities and peak frequencies is plotted by massive simulation data. This diagram can provide guidance of controlling particular frequency noises.A new general acoustical model for metal foam with gradient porosities, which is based on the Transfer Matrix Method and JCA model, is proposed in this paper. By comparing the results of the new model with simulation results, the new model is proved feasible to use.