说明：  对信号进行短时傅里叶变换和小波变换，观察其时频特性，压缩包中含有需要用到的测试信号文件，可以直接运行，供参考
(Carry out short-time Fourier transform and wavelet transform on the signal, observe its time-frequency characteristics, and the compression package contains the test signal files needed, which can be directly operated for reference)