The results we obtained on normal PCG signal show that the STFT analysis with different scale basis provides a clear comprehension of the cardiac events in both time and frequency domain.

实验结果表明，不同时频尺度的STFT分析可以很好地描述正常心音信号的时域和频域特征。

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Here, secondary treatment methods are introduced in detail, include time domain signal statistics character, frequency analysis fast Fourier transform (FFT), and short time Fourier transform (STFT).

这里，主要对二次处理的方法作了详细的介绍，包括时域信号的统计特征，频域分析的傅立叶变换和短时傅立叶变换。

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