The effective edge processing is the key to the performance of noise barrier. To prevent the sound diffraction within the low-medium frequency range, the quadratic residue diffuser (QRD) was combined with microperforated panel (MPP) in this study. The impedance of MPP with different parameters and QRD structure with N = 7 was calculated respectively and the matching degree of the composite structure was obtained. The insertion loss of noise barriers with different MPP-QRD top structures was field measured and compared to the equi-height vertical noise barrier. The results show that the degree of impedance matching between microperforated panels and quadratic residue diffusers is significantly correlated with their performance as the top structure of noise barrier. The acoustic impedance matched MPP-QRD top structure can significantly improve the insertion loss of the vertical noise barrierwith the same height. When the microperforated panel perforation is 3 %, the thickness is 0.8 mm, and the aperture is 0.6 mm, performance of the MPP-QRD structure is the best, the relative insertion loss can reach 4.07 dB.

中文翻译：

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MPP-QRD顶部结构声屏障插入损耗实验及声阻抗理论研究

有效的边缘处理是噪声屏障性能的关键。为了防止中低频率范围内的声音衍射，本研究将二次残余扩散器（QRD）与微穿孔板（MPP）相结合。分别计算不同参数的MPP和N=7的QRD结构的阻抗，得到复合结构的匹配度。对不同 MPP-QRD 顶部结构的隔音屏障的插入损耗进行了现场测量，并与等高垂直隔音屏障进行了比较。结果表明，微穿孔板和二次残余扩散器之间的阻抗匹配程度与其作为隔音屏障顶部结构的性能显着相关。声阻抗匹配的MPP-QRD顶部结构可以显着改善同高度垂直声屏障的插入损耗。当微穿孔板穿孔率为3%、厚度为0.8 mm、孔径为0.6 mm时，MPP-QRD结构的性能最佳，相对插损可达4.07 dB。