Broadband sound transmission loss of a large-scale membrane-type acoustic metamaterial for low-frequency noise control

Recent works have demonstrated the potential of small-scale membrane-type acoustic metamaterials for low-frequency (<500 Hz) noise control. Such a phenomenon is attributed to the resonant behavior of the overhanging membrane in each unit cell. Considering industrial applications, large-scale designs may be preferred. This study presents a large-scale (0.8 × 0.8 m²) membrane-type acoustic metamaterial (or the meta-panel), which was evaluated experimentally and verified numerically. Experimental results showed that a broadband sound transmission loss (STL) improvement could be achieved by the incorporated membrane (up to 7.4 dB at 380 Hz). Numerically, parametric studies showed that the broadband STL performance of the meta-panel was due to not only the resonant behavior of the overhanging membrane but also the resonant behavior of the sandwiched membrane along the boundaries of the unit cells. If properly designed, this resonant behavior of the sandwiched membrane could complement membrane-type acoustic metamaterials to achieve an extended good STL performance across a broader frequency bandwidth.