Design and manufacture of low-frequency acoustic absorption metamaterials with enhanced coupling characteristic

The current designs of low-frequency acoustic absorption metamaterials suffer from inadequate prediction accuracy and low efficiency. Herein, by integrating impedance theory with artificial neural networks, we propose an optimisation method of unit impedance correction (UIC). Meanwhile, a mutated honeycomb structure with teardrop-shaped apertures (MHSTA) fabricated by stereolithography is proposed, which can enhance the low-frequency coupling performance through rationally arranging the relative positions of the apertures. To verify prediction ability of the UIC method, the 50 mm-thickness typical structures of MHSTA are designed for two low-frequency ranges (220-500 Hz and 230-550 Hz). Compared with the simulation, the UIC result can reach the maximum relative error of 3.9% and the maximum absolute error of 0.033, which ensures the accurate prediction commendably. The experiment also demonstrates that the acoustic absorption coefficients are highly consist with the UIC result. This work provides a novel strategy of precise design for low-frequency acoustic absorption metamaterials.