Wide-angle broadband sound absorption of acoustic metasurface with composited porous structures

Efficient broadband noise mitigation by compact absorbers remains a longstanding pursuit in acoustic engineering. Here, a composite phase-gradient acoustic metasurface (AMS) is proposed to achieve broadband and wide-angle sound absorption. The AMS consists of four periodically arranged units, each integrating melamine foam with rigid partitions to couple phase manipulation with acoustic energy dissipation. The acoustic behavior of the melamine foam is characterized using the Johnson-Champoux-Allard model. A phase shift distribution of the AMS across the 1000 Hz to 3000 Hz frequency range is optimized through a genetic algorithm. Numerical simulations reveal that the AMS effectively suppresses higher-order diffraction modes by converting them into dissipative surface waves. Compared with conventional configurations, including a uniform porous layer, a segmented non-gradient structure, and a space-coiling design without porous materials, the AMS exhibits superior enhanced broadband absorption for incident angles up to ±70°. This design strategy offers a compact and efficient solution for broadband and wide-angle acoustic absorption, with potential for practical noise control applications.