为满足航空声衬在宽频范围内的声学特性研究与验证需求，研制了流管声学实验台，采用了三维直接提取法和管道声模态解耦方法。在最高Ma=0.14的切向流环境中，测试单自由度和双自由度声衬的声学性能，包括声阻抗和传声损失，测试频率最高可达10 kHz，覆盖航空发动机和辅助动力装置的主要噪声频段。实验结果显示，三维直接提取法可以有效地从多模态声场环境中提取出声衬的声阻抗，结合入射声模态分解技术和Prony方法的原理，提出声阻抗优选原则和优选方法，对多个展向模态和散射模态下的声阻抗进行优选，最终的声阻抗结果与模型预测值相符。传声损失能够反映出单/双自由度声衬在不同流速下降噪能力的变化规律，以及双自由度声衬在宽频降噪方面的优势。

To fulfill the requirements for researching and validating the acoustic characteristics of aviation acoustic liners across a wide frequency range， a flow tube acoustic test bench was developed， employing the three-dimensional straightforward method （3D-SFM） and the pipe acoustic mode decoupling approach. In a grazing flow environment with a maximum Mach number of 0.14， the acoustic performances of single- and double-degree-of-freedom acoustic liners， including acoustic impedance and sound transmission loss， were tested. The maximum test frequency could reach 10 kHz， covering the main noise frequency bands of aeroengines and auxiliary power units. The experimental results demonstrate that the 3D-SFM can effectively educe the acoustic impedance of the acoustic liner in a multi-modal sound field. Furthermore， based on spanwise mode decomposition and the Prony method， the optimization principle and methodology were proposed to optimize acoustic impedance under multiple spanwise modes and scattering modes. The final acoustic impedance outcomes exhibited excellent consistency with the prediction of liner’s impedance model. Sound transmission loss was capable of reflecting the variation law of the noise reduction capability of single/double-degree-of-freedom acoustic liners under different Mach numbers of grazing flow， as well as the advantages of double-degree-of-freedom acoustic liners in broadband noise reduction.