吸声侧壁对微穿孔共振结构声学性能的影响

在微穿孔共振结构的空腔侧壁铺设吸声层将增大空腔的声顺,引进空腔的声阻,从而明显改进结构的吸声特性。与对应的刚性壁面空腔结构相比较,吸声壁面结构的吸声系数共振峰频率降低,频响曲线平坦,峰-谷起伏减小。其特性与填满吸声材料的空腔结构基本相同。相应的理论公式得到实例的有力支持。与三维理论相比较,一维理论比较简洁,仅需引入材料的垂直入射吸声系数。其预测的共振结构吸声系数幅值能够满足工程设计的要求,但是没能充分反映吸声材料对共振峰频率的影响,预测的共振峰频率偏高。

Effects of absorbing wall on acoustical property of micro-perforated panel absorbers

With placing absorbing material on the side wall of cavity in a micro-perforated panel absorber,the acoustic compliance of cavity increases,and the acoustic resistance of cavity appears,thereby the acostic property of the mi-cro-perforated panel absorber is improved.Compared with an absorber structure with rigid wall,the resonant frequency of the structure with absorbing wall is lower,the absorption coefficient frequency response curve tends to flat,and the difference between peak and valley in the curve deceases.Its acoustical characteristics are basically the same as that of the structure filled up with absorbing material.Two theoretical calculation formulas has been derived and supported by an example.Pithier than three-dimensional formula,one-dimensional formula only requires normal incidence absorp-tion coefficient and can meet engineer accuracy except for higher resonance frequency.