空腔深度序列变化及腔内膜板拓展并联微穿孔低频吸声

In order to improve the acoustic absorption performance of micro-perforated panel structure at low frequency, the viewpoint is presented applying impedance coupling between parallel array of micro-perforated units as well as interior reaonator in cavity. Sound propagation theory in medias, sound scatter theory and finite element method are adopted jointly in the research to establish theoretical calculation model of compound structure of micro-perforated structures with interior membrane/panel resonant structure and with different cavity depths varying in sequences in one/two dimension. By theoretical models verified by measurement results, the effect of array mode of cavities, depth changing sequence of cavities, distribution and parameters of membrane/panel resonant structure to the sound absorption performance at low frequency are studied. Characteristics and rules of sound absorption performance of compounded micro-perforated panels at various conditions are to be investigated. Parameters with potential influence are to be identified and optimization design method of the compounded structure is to be presented. Fundamental scientific problems of acoustic absorption at low frequency are referred in the research. Study results of the research will supplement the acoustic theory of micro-perforated structures and explore the application of micro-perforated structures at low frequency. Study results also help to solve the difficulties of sound absorption at low frequency. The research has significant scientific importance and is of great value in realistic application.

针对微穿孔结构的低频吸声性能拓展问题，提出利用并联单元的阻抗耦合及腔内设置共振结构提高低频吸声。项目根据媒质间声传播理论、声散射理论和有限元法，建立腔内设置膜/板结构及空腔深度在一维/两维方向按不同序列变化的微穿孔板并联复合结构的吸声理论和计算模型。采用经试验研究校验的理论模型，从空腔的布置方式、空腔深度在一维/两维方向上的序列变化、空腔内膜板共振结构的分布和参量变化等方面对低频吸声性能的影响进行深入的理论和试验研究。研究结果将揭示不同声学条件对微穿孔板并联复合结构低频吸声性能的影响特性和内在规律，分析确定重要的影响参量，形成微穿孔并联复合结构的优化设计方法。研究涉及低频吸声的基础科学问题，成果对完善微穿孔复合结构的吸声理论、拓展微穿孔结构在低频的应用有重要科学意义，对解决目前低频吸声的难点问题有重要的应用价值。

本项目按计划对微穿孔并联结构进行研究，建立面板平齐的并联结构、背板平齐的并联结构、空腔深度按随机序列变化的并联结构、腔内复合薄板共振结构的并联结构的吸声计算模型，分析重要参量对吸声性能的影响特性和规律，提出具有宽频高吸声的优化并联结构。对于一维面板平齐的并联结构，考虑声阻抗不连续引起的散射，采用声散射理论进行计算，二维面板平齐并联结构综合考虑两个方向阻抗突变引起的散射场。对于背板平齐的微穿孔板并联结构，综合考虑声阻抗突变和结构表面不连续引起的散射。对于内含薄板的并联结构，考虑薄板空腔结构的声阻抗影响，采用声传播理论确定单体的复合阻抗，据散射理论进行计算。对于相同单体参数，背板平齐的并联结构吸声系数不一定比面板平齐的并联结构高，但吸声频谱曲线平坦。背板平齐结构的单体深度尺寸差异对吸声性能影响显著。含薄板空腔结构的微穿孔并联结构可以改善低频吸声性能，整体上吸声峰值向低频移动，峰值有所提高。微穿孔并联结构吸声性能的主要影响参数有单体的宽度、单体的周期、并联单体的共振频率及间距、并联单体的吸声系数峰值、并联单体的吸声频带宽度。在等宽度条件下，单体宽度越小，吸声性能越好。但宽度小于10cm时，随着宽度的减小，吸声性能的变化较小。并联单体的宽度比对吸声性能也有影响，等宽度的并联结构具有相对最佳的吸声性能。并联单体的吸声性能对结构的吸声性能有显著的影响，采用正交法针确定具有低频良好吸声的双空腔并联结构的参量范围。单体阻抗应匹配，声阻不宜过大。空腔深度序列对并联结构有影响，相对于双空腔结构，随机序列的空腔布置可提高吸声峰值，拓展低频吸声频带。随机序列的长度越长，频带越容易展宽。剩余二次序列的影响比M序列显著。研究得到在低频以下具有良好吸声性能的优化双空腔并联结构和随机序列并联结构，吸声频带接近3个倍频程，峰值超过0.9。研究中的并联结构计算模型尚未有文献，研究工作完善了微穿孔板吸声理论，拓展了微穿孔板的应用，尤其低频方面的应用，提出了新型低频吸声结构，对解决低频吸声的难点问题有重要的应用价值。