多孔材料声学参数辨识及其在城轨列车顶板隔声中的应用

摘要

针对城轨列车隧道运行车内噪声显著问题,对车体隔声薄弱的双层中空顶板结构,提出添加多孔材料的降噪结构优化.考虑到多孔材料声学参数直接测量存在困难,提出采用驻波管测试其吸声特性,然后基于声学参数辨识来确定的方法.基于传递矩阵法建立了轻量化城轨列车顶板结构隔声特性预测分析模型,计算分析3种典型多孔材料在顶板结构应用的隔声性能提高效果,调查了多孔材料厚度和安装位置对城轨列车顶板隔声性能的影响.研究结果表明:未作多孔材料降噪处理的顶板结构在315 Hz处存在显著的隔声低谷,通过多孔材料的添加应用,可有效提高该低谷隔声量和顶板整体隔声性能;多孔材料厚度越大降噪效果越好,但其随厚度并非线性变化,考虑到经济成本,采用16.5 mm效果最佳;多孔材料安装方案的影响不明显,建议将多孔材料放置在靠近铝板的任意一侧安装;相关结果可为典型的轻量化城轨列车降噪提供科学参考.%Structure optimization of adding porous materials to the double-layer hollow ceiling of metro trains with weak sound insulation ability was proposed to alleviate the serious interior noise when the metro trains were running in tunnels. Considering the difficulty of direct measurement of sound absorption characteristic of the porous materials, acoustic parameters were tested and then identified by the impedance tube tests and the acoustic parameters identification method. Sound insulation characteristics analysis model for a lightweight metro ceiling was established based on the transfer matrix method. The improvement of the sound insulation performance of metro ceilings filled with three typical porous materials was analyzed, and the effects of the porous materials' thickness and installation location on the sound insulation properties were investigated. The results show that the ceiling structure without noise reduction porous material has a sound insulation valley at 315 Hz. Adding porous material can not only effectively improve sound insulation performance at the sound insulation valley but also improve the overall sound insulation performance. It is shown that the noise reduction increases nonlinearly with the increase of the layer thickness of the porous materials. Taking cost into consideration, the optimal thickness of porous material is 16.5 mm. The effects of the porous material installation location on the sound insulation is not significant. It is recommended that the porous material should be placed close to either side of aluminum plate. The results of this study can provide a quantitative reference for the noise reduction of the typical lightweight metro train.