Dual-directional high sound absorption design utilizing multi-scale composite metamaterial for applications in both water and air

This study introduces a multi-scale composite metamaterial capable of simultaneously achieving dual-directional sound absorption in both air and water. Following optimization through teaching–learning-based optimization algorithms, the composite metamaterial demonstrates an average sound absorption coefficient of 0.9811 in air and 0.828 in water in the frequency range of 1 Hz to 10 kHz, representing increases of 75.79% and 177.57%, respectively. Moreover, the optimized design reduces the thickness by 7.5 mm, offering crucial insights for the silent design of marine equipment.