Prediction of the effect of porous sound absorbing material inside a coupled plate cavity system
This paper predicts the acoustic properties of the porous sound absorbing material in a box cavity by conducting a finite element method (FEM) analysis, and it verifies the estimated acoustic properties using an appropriate experimental method. The cavity is a rectangular box with five rigid walls and one flexible wall which is an aluminium plate. The porous sound absorbing material is attached to the inner surface of the plate, in order to modify the coupling between the plate inner surface and the air inside the box. The plate is mechanically excited by using an electromagnetic shaker, which is imitating structure borne noise. The generated noise is recorded by using pressure microphones at the different locations inside the box. The results show that there is good agreement between the FEM prediction and the measurement for the acoustic response at different locations inside the rectangular box. Sound pressure peaks due to cavity modes are effectively reduced by adding porous sound absorbing material. Furthermore, sound level in the cavity is reduced by a similar amount in both the numerical simulation and the measurement, when a porous sound absorbing material is added. The developed FEM model is used to characterise the effects of porous sound absorbing material in reducing the structure borne radiated noise.