说明：  低通滤波容许低频信号通过, 但减弱[或减少]频率高于截止频率的信号的通过。对于不同滤波器而言,每个频率的信号的减弱程度不同。
(Low-pass filter allows low-frequency signals, but weakened [or decrease] the frequency higher than the cut-off frequency of the signal through. For different filter for each frequency of the signal weakened to different degrees.)