A 低通 滤波器 lets the 贝斯 音调 through the 低 频率 and removes the treble 高 频率 The separation between 低 and 高 频率 is called the cut-off 频率 If the cut-off 频率 is 500 赫兹 赫兹 all of the 频率 over 500 赫兹 will disappear