We designed a composite loaded sound absorber (CLSA) composed of a sub-wavelength Helmholtz resonator and porous material, which was loaded on the side branches of a rectangular tube. Based on the transfer matrix method, an equivalent acoustic model was established to calculate the acoustic performance of the absorber. According to the equivalent acoustic model and critical coupling theory, a loaded absorber with thickness of 51 mm and perfect absorption at 156 Hz was achieved using the complex frequency plane analysis method (CFPM). The finite element simulation and acoustic experiment results verified the perfect sound absorption effect of the absorber at low frequencies. To overcome the defects of single frequency and narrow band of the perfect absorber, we designed nine different porous perfect absorber units that could achieve perfect sound absorption between 160 Hz and 312 Hz. Different numbers of porous perfect absorbers were placed on the side branch of the rectangular tube, and a broadband quasi-perfect sound absorption of more than 0.9 between 160 Hz and 285 Hz was realized by optimization. The experimental results further verified the quasi-perfect sound absorption effect of the CLSA. The theoretical model of low-frequency broadband quasi-perfect sound absorber and the design of a CLSA in this study provide a new possibility for the reduction of low or medium frequency noise in the tube.

我们设计了一种复合加载的吸声器（CLSA），它由亚波长的亥姆霍兹谐振器和多孔材料组成，并被加载在矩形管的侧支上。基于传递矩阵法，建立了等效的声学模型来计算吸收体的声学性能。根据等效声学模型和临界耦合理论，使用复频平面分析方法（CFPM）获得了厚度为51 mm且在156 Hz时具有完美吸收的负载吸收器。有限元模拟和声学实验结果验证了低频吸收器的完美吸声效果。为了克服理想吸收器的单频和窄带的缺陷，我们设计了九种不同的多孔完美吸收器单元，它们可以在160 Hz至312 Hz之间实现完美的声音吸收。在矩形管的侧支上放置了不同数量的多孔完美吸收体，并通过优化在160 Hz和285 Hz之间实现了0.9以上的宽带准完美吸声。实验结果进一步验证了CLSA的准完美吸声效果。本研究中的低频宽带准完美吸声器的理论模型和CLSA的设计为降低管中低频噪声提供了新的可能性。通过优化实现了在160 Hz和285 Hz之间的9。实验结果进一步验证了CLSA的准完美吸声效果。本研究中的低频宽带准完美吸声器的理论模型和CLSA的设计为降低管中低频噪声提供了新的可能性。通过优化实现了在160 Hz和285 Hz之间的9。实验结果进一步验证了CLSA的准完美吸声效果。本研究中的低频宽带准完美吸声器的理论模型和CLSA的设计为降低管中低频噪声提供了新的可能性。