Tunable acoustic composite metasurface based porous material for broadband sound absorption

This work designs a tunable acoustic composite metasurface, with porous material and a modified microperforated panel (MPP) system. The broadband sound absorption performance of the composite metasurface is evaluated by the analytical theory, numerical simulation, and experiment in the frequency range between 200 Hz and 3500 Hz. The designed composite metasurface has a significant advantage in sound absorption performance compared with a uniform porous material, especially in the low-frequency range. The excellent sound absorption performance is achieved not only by the wavefront controlling with the phase gradient adjustment but also by the resonance dissipation of the modified MPP system. The high-order reflected waves have been converted into surface waves by the wave controlling ability of the designed metasurface for excellent sound absorption at the high frequency of interest. The modified MPP system is formed by a microperforated panel and a coiling-up space cavity to achieve excellent sound absorption in the low-frequency range. By adjusting the length of the coiling silt in the modified microperforated panel system, the absorption peak can move to the frequency of interest. The compact composite metasurface with 3 cm height has remarkably improved the sound absorption of porous material alone from low to high frequency, which could easily replace porous material for better sound absorption in industry.