Figure 5. The apparent negative reflection behavior of the gradient acoustic metasurface when ξ = −1.016 k₀.

(a) The relation between the incident angle and reflected angle when k_s = −1.016. (b) Calculated scattered acoustic field under the plane acoustic wave illumination of different incident angle values when k_s = −1.016. The acoustic plane wave is incident at 15°, −15°, 30°, −30°, 45° and −45°, the beam would reflect at −49°, 49°, −31°, 31°, −18° and 18° correspondingly.