一种新型复合结构的垂直入射和扩散域声学性能机理研究

Study on the Acoustic Performance Mechanism of a New Type of Composite Structure in Vertical Incidence and Diffusion Domain

多层复合材料的设计是为了满足,不同噪声环境中的降噪需求,从而使设计人员根据材料的声传递特性设计合理的多层吸、隔声结构。以新型汽车防火墙多层复合结构为研究对象,建立了平面波在单-双层介质中的传播方程,通过数值仿真和阻抗管声学实验方法,分析了包含PU泡沫+EVA+吸音棉的传统多层结构与包含超细纤维多层结构中,空气夹层声传递规律。对比了热特征长度、黏性特征长度等参数对复合结构声学影响规律,同时,对多层复合结构组成的双面墙传递特性进行了分析。研究结果表明,在中高频区域,随着中间空气层厚度的增加,传统复合结构与超细纤维复合结构的声传递损失无显著变化;包含超细纤维多层结构在固有频率以内,吸声系数较小,而传统多层结构对于弯曲度、黏性特征长度、热特征长度等参数影响显著。在多层结构组成的双面墙结构中,在中频范围内,空腔厚度对声传递特性的影响较为显著,多层结构声传递损失随空腔厚度的增加逐渐增大。

The multi-layer composite material is designed to meet the noise reduction requirements in different noise environments,so that designers can design a reasonable multi-layer absorption and sound insulation structure according to the sound transmission characteristics of the material.The multi-layer composite structure of automobile firewall is taken as the research object,and the propagation equation of plane wave in single-double layer medium is established.Through numerical simulation and impedance tube acoustic experiment,the sound transmission law of air sandwich in traditional multi-layer structure including PU foam+EVA+sound-absorbing cotton and multi-layer structure including ultrafine fiber is analyzed.The effects of thermal characteristic length and viscous characteristic length on the acoustic properties of composite structures are compared.The results show that,there is no significant change in the acoustic transfer loss between the conventional composite structure and the superfine fiber composite structure with the increase of the thickness of the intermediate air layer in the medium-high frequency region.The multi-layer structure containing superfine fiber has a small sound absorption coefficient within the natural frequency,while the traditional multi-layer structure has a significant influence on the parameters such as bending degree,viscosity characteristic length and thermal characteristic length.In the two-wall structure composed of multi-layer structure,the influence of cavity thickness on sound transmission characteristics is significant in the medium frequency range,and the sound transmission loss of multi-layer structure increases gradually with the increase of cavity thickness.