首先，生成一个多音正弦，然后进行补零的插值，然后把补零插值的信号塞到一个低通滤波器里面，这样就有三个版本的信号，原始信号，补零插值信号，以及插值滤波之后的信号。(First, generate a polyphonic sine, and then make zero interpolation, and then fill the zero interpolation signal into a low-pass filter inside, so there are three versions of the signal, the original signal, zero interpolation signal, and interpolation filter After the signal.)