中文摘要：

叶片通过频率分量是风扇噪声的主要成分，但在对噪声测量信号进行频谱分析中发现选择不同带宽可导致显著不同的叶片通过频率分量谱值。讨论了使用不同带宽对相同风扇噪声记录进行的快速傅里叶变换（FFT）分析过程，由于FFT分析得到的频谱声压级是带宽内谱能量和，当由于转速波动引起的叶片通过频率波动范围超过分析带宽时带宽的变化将引起声压级的差异，本文提出了获得确定声压级频谱的方法。

英文摘要：

Components of Blade Passing Frequency （BPF） are the important elements of fan noise. In the spectrum analysis of noise signal, it was discovered that different analysis bandwidth made a significant difference in the BPF component value. In this paper, the Fast Fourier Transform （FFT） processes with different bandwidth for the same record of noise were discussed. Because the result of SPL is the energy sum within a bandwidth, while the range of BPF variation due to the varying rotating speed exceeds the bandwidth, the variation of bandwidth will make the SPL different. Finally, a method for determining the fan noise spectrum was introduced.