Broadband, high-sound-insulation honeycomb acoustic metastructure enabled by synergistic enhancement of membrane anti-resonance and Helmholtz resonance

The inherent conflict between low mass and high sound insulation presents a critical bottleneck in the development of advanced honeycomb structures for engineering applications. To address this, a broadband yet high-sound-insulation honeycomb acoustic metastructure is proposed by synergistically coupling membrane anti-resonance with Helmholtz resonance for the first time. A theoretical model is developed based on the space-harmonic expansion method to predict its sound transmission loss, and is validated against both finite element simulations and impedance tube measurements. The results demonstrate that the proposed metastructure achieves superior broadband insulation, with its STL significantly exceeding the mass law prediction over multiple frequency bands. Specifically, the synergistic enhancement mechanism is verified by evaluating the cross-sectional energy flux. Furthermore, the theoretical bound of the synergistic enhancement is determined analytically. Moreover, parametric studies are conducted to confirm the tunability and the robustness of the proposed design method. Finally, given in practical engineering applications, the proposed metastructure is applied to a soundproof enclosure. Compared with the traditional honeycomb enclosure, the radiated sound pressure level of the soundproof enclosure has been reduced by 45.5 dB at the single line spectrum, and the A-weighted sound pressure level in the external environment within 500 Hz-2000 Hz has been reduced by 4.1 dB. This work provides new physical insights into coupled acoustic metamaterials and offers a viable pathway toward multifunctional structural–acoustic integration.