Figure 6. The apparent negative reflection behavior of the gradient acoustic metasurface when ξ = −1.307 k₀.

(a) The relation between sin θ_i and sin θ_re when k_s = −1.307. The blue solid line represents the anomalous reflection , the pink solid line represents specular reflection and the cyan solid line represents the apparent negative reflection . (b) The relation between the incident angle and reflected angle when k_s = −1.307. (c) Calculated scattered acoustic field under the plane acoustic wave illumination of different incident angle values when k_s = −1.307. The acoustic plane wave is incident at 10°, −10°, 30° and −30°, and the beam reflects at 10°, −10°, −53° and 53° correspondingly.