Abstract Calculation of noise reduction and acoustic impedance of the duct system is needed for the one-port source model, which is widely used in the field of duct acoustics for extracting the source characteristics and predicting the radiating noise at the open end. The flow field in the duct influences the acoustic characteristics when the flow velocity is relatively high. Recently, the time domain method has been adopted to study the flow effects on the acoustic response of the duct mufflers. However, the existing method only focuses on the calculation of transmission loss (TL) or transfer matrix. In this paper, a modified time domain approach is proposed for the first time to calculate the noise reduction and acoustic impedance of the intake duct system. In the proposed time domain model, the frequency dependent reflection at the intake port, rather the anechoic boundary used for TL calculation, is simulated by simply adding a correction pipe at the port. This approach has effectively simplified the implementation of the traditional time domain method in dealing with frequency dependent reflection at the open end. The porous sound-absorbing material commonly used in the intake system is modelled by modified equations with the material porosity and flow resistivity. The predicted time-domain sound pressure signals are then post-processed to obtain the noise reduction and the acoustic impedance in a different way from the traditional time domain TL calculation approach. The result of validation has shown that the noise reduction and acoustic impedance predicted with the modified time domain approach agree well with the measured results and the results calculated from frequency domain methods in the cases without and with meanflow.

中文翻译：

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一种改进的时域计算进气管道系统降噪和声阻抗的方法

摘要 单端口声源模型需要计算管道系统的降噪和声阻抗，广泛应用于管道声学领域，用于提取源特征和预测开放端的辐射噪声。当流速较高时，管道中的流场会影响声学特性。最近，已采用时域方法来研究流动对管道消声器声学响应的影响。然而，现有的方法只关注传输损耗（TL）或传输矩阵的计算。在本文中，首次提出了一种改进的时域方法来计算进气管道系统的降噪和声阻抗。在建议的时域模型中，进气口处的频率相关反射，相反，用于 TL 计算的消声边界是通过简单地在端口添加校正管道来模拟的。这种方法有效地简化了传统时域方法在处理开放端频率相关反射时的实现。进气系统中常用的多孔吸声材料通过修改后的方程与材料孔隙率和流阻率进行建模。然后对预测的时域声压信号进行后处理，以不同于传统时域 TL 计算方法的方式获得降噪和声阻抗。