说明：  C语言实现设计的FIR滤波器,带通提取该频率信号，带阻是限制该频率信号。采样频率22050Hz，自己确定通带宽度，一般信号通带（或阻带）在200～300Hz，通带内衰减1db，过渡带在100～250Hz，阻带内衰减30db。
(C language design FIR filter,Bandpass frequency signal extracted with resistance is to limit the frequency of the signal. Sampling frequency 22050Hz, itself the passband width, general signal passband (or stop band) at 200 ~ 300Hz, the passband attenuation 1db, transition zone at 100 ~ 250Hz, stop-band attenuation of 30db.)