Porous acoustic metamaterials in an inverted wedge shape

This study systemically applies porous acoustic metamaterials in an inverted wedge shape on the planar interface. The porous acoustic metamaterials have been studied analytically, numerically, and in the laboratory. Results indicate that the new porous acoustic metamaterials based on melamine foams demonstrate anomalous reflection phenomena and possess better sound absorption properties in a wide range of frequencies and incidence angles than uniform melamine layers and the classic wedge shape absorbers with the same weight. Several metasurfaces with different periodical lengths are also discussed to improve their sound absorption properties further. In the porous acoustic metamaterial design, the wave manipulation can be well achieved regardless of the properties of porous materials as long as the desired reflected phase shifts are realized on the reflected surface, which creates a new way to increase the sound absorption properties of classic absorbing foams.