Ultra-broadband acoustic absorption of a thin microperforated panel metamaterial with multi-order resonance

Abstract Aiming at poor efficiency of the traditional materials in low-mid frequency sound absorption and its narrow bandwidth, we present an ultra-broadband acoustic metamaterial that can achieve near-perfect continuous absorption within 380 Hz–3600 Hz with a thickness of only 7.2 cm. Its basic cell is constructed by turning the original neck of a Helmholtz resonator into multiple smaller ones, and the neck panel becomes into a micro-perforated panel (MPP). By coupling the characteristics of the cavity’s multi-order resonance and the MPP’s broadband absorption, the cell’s high-order impedances can be tuned to more match that of the air medium. The cell can therefore obtain multiple excellent high-order absorption peaks besides the original one; meanwhile all the peaks can become broader resulting from the larger energy leakage rate. On this basis, a subwavelength 12-cell sample is obtained of which the absorption band is broadened almost 100% by the high-order peaks and has an average absorption coefficient above 90%. Characterized by the extraordinary absorption performance, thin thickness, and easy-fabricated structure, this proposed metamaterial has great potential in noise control engineering applications.