运用弹性支撑背板提高微穿孔板低频吸声性能

Low-frequency sound absorptivity improvement of micro-perforated panel absorber by elastic supported back-wall

为了提高微穿孔板结构的低频吸声性能,将传统微穿孔板结构的刚性背板改进为弹性支撑背板,通过理论计算和试验对这一改进进行研究.由等效电路图推导出弹性支撑背板单元的矩阵,运用传递矩阵方法,将其和空腔单元矩阵、微穿孔单元矩阵进行串联,建立新结构的理论模型.通过振动试验测量弹性支撑背板的阻尼系数和刚度系数,计算出结构的吸声系数,并与驻波管试验的测量结果对比.结果表明:理论计算和试验结果吻合良好;改进设计的微穿孔板结构同时利用了微穿孔板的腔共振吸声和背板的机械阻抗吸声作用,能够在不增加结构厚度的情况下提高低频吸声性能,并且同时保持中高频吸声效果.

In order to improve low-frequency sound absorptivity, the basic structure of rigid back-wall in MPA was substituted by elastic support back-wall. The improvement was investigated through theoretical calculation and experiments. The matrix of elastic support back-wall 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 back-wall 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 Helmholtz-resonance and mechanical impedance sound absorption. The low-frequency sound absorptivity is improved without increasing of total structure length and the middle and high frequency sound absorptivity can be kept invariant.