An Ultra-Thin Composite Metasurface with Hybrid-Damping Modes for Broadband Sound Absorption

In this paper, we proposed an ultra-thin composite metasurface for broadband sound absorption, in which a compound Helmholtz structure and porous materials are coupled in a parallel-series arrangement. The Helmholtz structure comprises multiple compound cells with hybrid-damping modes, in which the over-damping and matched-damping impedance are integrated for a lower and broader absorption spectrum. By coupling the porous materials, the metasurface obtains above 85% average absorption over 750–10,000 Hz with a thickness of 31 mm, and the performance below 1600 Hz is significantly enhanced compared to the pure porous materials. This metasurface could possess broad applications in modern equipment considering its extraordinary absorption and compact structure.