风扇管道宽频噪声的声功率和远场指向性研究

Research on sound power and far-field directivity of fan ducted broadband noise

针对风扇管道宽频噪声,利用两传声器模态分解方法对风扇宽频噪声模态分解、声功率测量以及远场辐射特性进行了研究,与需要较多数量的传声器阵列测量方法相比,这种优势在高频管道宽频噪声测量上尤为突出。本文针对该方法的有效性和准确性进行了数值研究,并基于轴流风扇试验台实验验证了该方法的精确性。该方法预测出的声功率与理论值完全吻合。风扇噪声实验结果表明两传声器方法在声功率方面有较高的准确性,最大误差为3 dB,其预测的远程辐射指向性在20°~60°范围内能较为准确地捕捉风扇进口端远场噪声辐射特征,但需要指出的是其预测精度对传声器间距非常敏感,小间距麦克风测量的相关性特征更加稳定,促使其预测精度比间距更大的结果更高。

For the fan ducted broadband noise,a two-microphone modal decomposition method was used to study the fan broadband noise modal decomposition,sound power measurement and far-field radiation characteristics.Compared with the measurement method requiring a larger number of microphone arrays,it is especially prominent in the measurement of broadband noise in high frequency pipelines.A numerical study on the effectiveness and accuracy of the method was carried out,and the accuracy of the method was verified based on the axial fan experiment.The sound power predicted by this method was in perfect agreement with the theoretical value.The experimental measurement results of fan noise showed that the two-microphone method had high accuracy in terms of sound power,and the maximum error was 3 dB.The predicted radiation directivity can accurately capture the far-field noise radiation characteristics of the fan from 20 to 60 degrees,but it should be pointed out that its prediction accuracy was very sensitive to the micro-phone spacing,and the correlation characteristics of smallspacing microphone measurements were more stable,making its prediction accuracy higher than results with larger spacing.