Experiments on reflection and transmission of acoustic porous metasurface with composite structure

A composite structure made by a metal-based porous material, namely porous metasurface here, is designed for good sound absorption performance considering both reflection and transmission. The proposed configuration is a periodic structure containing four slits filled with the porous samples with different thicknesses in one period. Through designing the thicknesses of porous samples, linear phase gradients are generated on reflected and transmitted surfaces respectively, which play key roles for the reflected and refracted behaviors. Using the diffraction theory, the associating behaviors are predicted analytically and also validated by simulations and laboratory tests. Good agreements add confidence on the studies of sound absorption performance. Through adjusting the period length, the good sound absorption can be obtained over a wide range of incident angles at the designed frequency. The proposed composite structure has potential to be applied for noise isolation and sound absorption, where sound transmission is unavoidable.