用奇阶互补法设计四带滤波器组；并画出其频响。滤波器设计参数为：Fp＝1.7KHz, Fr＝2.3KHz, Fs＝8KHz, Armin≥70dB。 part2-Designed four-band filter group　complementary use of odd order, and draw its frequency response. The filter design parameters: Fp = 1.7KHz, Fr = 2.3KHz, Fs = 8KHz, Armin ≥ 70dB. part2