说明：  利用C++编写的低通滤波函数。采用快速傅里叶的方法对信号进行处理。希望能够帮组带大家。如有不足，请多多包含哈
(Using C++ to write low-pass filter function . The method of using fast Fourier transform signal processing . Want to help the group with everyone . If insufficient, please include Kazakhstan)