Considering the unit cell cross-sectional area (*S* = 1 m^{2}) and the periodical spacing between each unit cell to be *d* = 1 m, to make the adjacent impedance rate $\alpha =2$ at the frequency $f=5\u2009Hz$, the effective density and effective Young's modulus are chosen as: $\rho eff1$ = 16 kg/m^{3}, $Eeff1$ = 640,000 Pa, for the first section; $\rho eff2$ = 4 kg/m^{3}, $Eeff2$ = 640,000 Pa, for the second section; $\rho eff3$ = 1 kg/m^{3}, $Eeff3$ = 640,000 Pa, for the third section. Based on Eq. (40), $k1$ and $k2$ can be obtained as: *k*^{1}_{1} = 643,947 N/m, *k*^{1}_{2} = 6579.7 N/m, for the first section; *k*^{2}_{1} = 640,987 N/m, *k*^{2}_{2} = 13,159.5 N/m, for the second section; and *k*^{3}_{1} = 640,247 N/m, *k*^{3}_{2} = 14,412.8 N/m, for the third section. In addition, to satisfy the condition of the maximum value of Amp(*A*_{N}), we set $\omega t1=\pi /2$ and $\omega t2=\pi $, and the lengths of first two sections can be calculated as *L*_{1} = 10 m and *L*_{2} = 40 m.