Design, analysis, and experimental validation of a sonic black hole structure for near-perfect broadband sound absorption

Abstract

Based on the benefits brought by the slow-sound effect and structural optimization design, we propose an enhanced sonic black hole (SBH) structure for low-frequency, broadband sound absorption. The proposed SBH consisting of five basic absorption units (BAUs), each of which includes a micro-perforated plate, a folded cavity, a slit and a trapezoidal cavity. This design features the micro-slit structure with the aim of producing additional resonance peak for broadband sound absorption. A theoretical method that integrates volume decomposition and coupling method (VDCM) and transfer matrix method (TMM) is proposed to predict absorption characteristics of the SBH. The data-driven Kriging surrogate technology is used to make the developed theoretical models very accurate in predicting absorption characteristics. On this basis, the optimal sizes of five BAU cavities are obtained by genetic algorithm (GA). The sound absorption coefficient of the optimized SBH structure is evaluated using theoretical formulas, finite element simulation and experimental measurements, good agreement is found. Numerical and experimental results demonstrate that the optimized SBH exhibits an absorption coefficient exceeding 0.9 within the frequency range of 100 ∼ 1600 Hz, showing a near-perfect broadband absorption. This study provides a fast, effective method for the design of the SBH structure aiming at sound absorption applications.