结合机械阻抗的微穿孔板吸声计算及试验研究

机械阻抗板(MIP)由刚性薄板与其周围黏贴的阻尼材料组成,利用其机械共振将声能耗散于黏性阻尼,阻抗板与微穿孔板相结合可提高传统微穿孔板(MPP)的低频吸声性能。计算组合结构吸声系数的关键是阻抗板后封闭空腔的处理,对比分析了将空腔等效成声顺,阻抗转移法,传递矩阵法及将空腔等效成空气弹簧的4种处理方法,并进行了相应的试验验证。研究表明,将空腔等效成声顺和空气弹簧实质上是相同的,但当空腔深度较大时,由于忽略声质量,易产生计算误差。阻抗转移法与传递矩阵法实质上是相同的,与试验结果吻合良好,计算准确。

Acoustic Calculation and Experimental Research of Micro perforated Panel Combined with the Mechanical Impedance

The mechanical impedance plate (MIP) consists of one piece of thin plate and viscoelastic material. Based on the mechanism of mechanical resonance absorption, sound energy in low frequency will be effectively absorbed by the boundary viscous damping. Performance of low frequency sound absorption is improved by the combination of micro perforated panel and mechanical impedance plate. The key to compute the absorption coefficient of the composite structure is to deal with the closed cavity behind the impedance plate. Comparative analysis is made with four methods which are the closed cavity being equivalent to acoustic compliance; transfer matrix method; impedance transfer method; the closed cavity being equivalent to air spring. The corresponding experiments are carried out for verification. The results show that the closed cavity being equivalent to acoustic compliance or air spring is essentially identical. But when the depth of the cavity is large, the calculation error will appear because of ignoring the sound mass. The transfer matrix method and impedance transfer method are essentially identical. Theoretical calculation shows good agreement with the experimental results. Results of calculation are accurate.