现场测量管道声衬声阻抗的双传声器法实验研究
An experimental investigation of two-microphone method for in situ measurement of the acoustic impedance of a duct liner
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摘要: 对现场测量管道声衬声阻抗的双传声器法进行了研究.为解决实用声衬蜂窝单元尺寸过小,无法直接嵌入常用传声器的难题,采用了探针传声器技术,通过外径1.5mm的细管引出不易直接测量的声衬表面和背腔内声压信号,并设计了校准方法以确保测量精度.进而,在管内声场具有多重模态和声波斜入射的条件下,应用双传声器法测量了实用蜂窝夹层声衬的声阻抗,并与标准阻抗管的测量数据和一种理论预测模型进行了对比,结果符合良好,从而验证了本方法及测量装置的可靠性.Abstract: The two-microphone method is investigated for the objective of in situ measuring the impedance of an acoustic liner in a duct.In order to avoid the influence caused by directly inserting the comparatively large microphones into a practical acoustic liner typically consisted of small honeycomb cells,the probe tubes as small as 1.5 mm in diameter are used to conduct the sound pressure at the liner surface and that at the back plate to the microphones.Acalibration method is designed to ensure high measurement accuracy of the thus-formed probe microphones.By the use of the two-microphone method,the acoustic impedance of a honeycomb-structure acoustic liner is measured when exposed to the sound waves at oblique incidences inside a duct.The measurement result is compared with the data obtained on a standard impedance tube and the prediction of an existing impedance model.The reliability of the present two-microphone method is validated by the good agreement between the different results.
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