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首页> 外文期刊>Journal of Sound and Vibration >Straightforward impedance eduction method for non-grazing incidence wave with multiple modes
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Straightforward impedance eduction method for non-grazing incidence wave with multiple modes

机译：具有多种模式的非放牧发射波的直接阻抗进展方法

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摘要

The control of modern aeroengine noise poses great challenge to the design of acoustic liners, due to the existence of multiple higher-order modes over a very wide frequency range in acoustic nacelles. In order to meet the pressing demand, the straightforward impedance eduction method is further developed such that it can be applied to more general acoustic environment where there are both plane mode and higher-order modes incident upon a test liner. A novelty of the present method is using a diagonally mounted microphone array on the opposite wall of the test liner in a flow duct, thus the measured wall sound pressure simultaneously contains the information of the modes in both the axial and transverse directions. Then, the employment of Prony's method enables the realization of the full modal decomposition to the acoustic field in the flow duct. Numerical experiments simulating acoustic fields with a finite element model are conducted to investigate and validate the feasibility of the present method for both a small-scale and a large-scale flow ducts. Two ceramic tubular liners and a perforated liner are tested as specimens, whose impedance values to be educed are known a priori by means of existing impedance models. Random perturbation is added into the acoustic field data to simulate realistic noisy acoustic environments. The results show that the present method can educe the imposed impedance with a good accuracy when the liner specimens are subjected to the sound field composing of multiple incident modes including several transverse modes in both ducts. The frequency scope of the impedance eduction is considerably extended when compared with the methods restricted by the assumption of plane incident mode, with the upper frequency reaching up to 6.0 kHz and 5.0 kHz for the ducts, respectively. A parametric study indicates that the accuracy of impedance eduction can be promoted by increasing the signal-to-noise ratio and the number of microphones. (C) 2018 Else
机译：由于在声学烟囱中的非常宽的频率范围内，现代航空发动机噪声的控制对声学衬里的设计产生了极大的挑战。为了满足按下需求，进一步开发了直接的阻抗进一步发展方法，使得它可以应用于更多的通用声学环境，其中存在在测试衬里上发生的平面模式和更高阶模式。本方法的新颖性在流动管道中使用对角上安装的麦克风阵列在测试衬里的相对壁上，因此测量的壁声压力同时包含轴向和横向方向上的模式的信息。然后，掌上的就业方法使得能够实现流量管道中的声场的全模态分解。进行模拟具有有限元模型的声场的数值实验，以研究和验证本发明方法对小规模和大型流动管道的可行性。两个陶瓷管状衬垫和穿孔衬垫被测标本，其阻抗值通过现有阻抗模型已知优先。随机扰动被添加到声场数据中以模拟真实的嘈杂声学环境。结果表明，当衬里样本经受多种入射模式的声场构成时，本方法可以以良好的精度向施加的阻抗发射良好的阻抗，包括两个管道中的几种横向模式。与通过平面入射模式的假设限制的方法相比，阻抗进出的频率范围显着延伸，其上频率分别达到6.0kHz和5.0kHz的管道。参数研究表明，通过增加信噪比和麦克风的数量，可以促进阻抗的准确性。 （c）2018否则

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