Figure 3. Robustness of the cloaking effect against the deviation of the material parameters of the cloak.

(a,b) Acoustic field distributions for the cases in which the structure parameters are identical same with cases (a,b) in Fig. 2, except that the mass densities for layers 1 and 2 of the dual-layered structure are set to be 0.5 ρ₁ and 0.5 ρ₂ respectively. (c,d) Acoustic field distributions for the cases in which the structure parameters are identical with cases (a,b) in Fig. 2, except that the moduli for layers 1 and 2 of the dual-layered structure are set to be 1.5 κ₁ and 1.5 κ₂ respectively. (e) Total scattering cross sections of the same scatterer protected by four different cloaks: cloak in case (a) (red line), cloak in case (b) (blue line), cloak in (a) (red dashed line) and cloak in (b) (blue dashed line). (f) Total scattering cross sections of the same scatterer protected by four different cloaks: cloak in case (a) (red line), cloak in case (b) (blue line), cloak in (c) (red dashed line) and cloak in (d) (blue dashed line).