CPA realized by DMR. (a) The reflection (black), transmission (blue), and absorption (red) coefficients for the DMR under one-side incident. (b) The scattering (black) and absorption (red) coefficient under the CPA scenario, i.e., when two beams of sounds come from both sides with the same amplitude but opposite phase as shown in (c). The solid lines are from theoretical calculation based on the eigenmode in (d) and the open circles from numerical simulations. (c) The schematic illustration of the CPA scenario. (d) The simulated cross-sectional profile of the DMR’s 1st resonance that satisfies the CPA requirement.