Abstract：In order to improve lowfrequency sound absorptivity, the basic structure of rigid backwall in MPA was substituted by elastic support backwall. The improvement was investigated through theoretical calculation and experiments. The matrix of elastic support backwall was deduced by equivalent circuit diagram and connected in series with cavity matrix and micropore by transfer matrix method to establish a new structure theoretical model. The damping coefficient and stiffness coefficient of the elastic support backwall were measured by vibration test, and the acoustic absorptivity was calculated and measured by standing wave tube test. The results show that the theoretical calculation is in good consistency with the experimental results. The new structure has both Helmholtzresonance and mechanical impedance sound absorption. The lowfrequency sound absorptivity is improved without increasing of total structure length and the middle and high frequency sound absorptivity can be kept invariant.
2012, Vol. 33 
