Tensegrity structure-inspired tunable membrane-type acoustic metamaterials: Conceptual design, fabrication, and performance investigation

Membrane-type acoustic metamaterials (MAMs) have garnered significant attention owing to their thin-walled, lightweight nature and exceptional capabilities in low-frequency sound insulation. In particular, tunable MAMs offer several advantages in acoustic performance, enabling precise adaptation to varying external noise excitations. In this study, we present a novel design of tunable MAMs inspired by tensegrity structures. These MAMs feature adjustable rods that induce controlled deformation in the membrane, generating membrane prestress distributions to achieve tunable sound insulation properties. By implementing simultaneous deformation control with multiple rods, we aim to establish complex membrane prestress distributions, thereby broadening the attenuation frequency range and enhancing the overall tunability of the system. Through meticulous material selection and structural design, we fabricate specimens of the tunable MAMs. Impedance tube experiments and the structural-acoustic coupled finite element method are adopted to validate the performance and tunability of the proposed design, uncovering the sound insulation mechanism related to anti-resonance. To further enhance sound insulation performance without significantly adding weight or volume, we develop a double-membrane tunable MAM using a stacking strategy. Experimental results reveal that the sound transmission loss of this double-membrane tunable MAM exhibits a distinctive multi-peak pattern in the frequency range above 200 Hz, with the sound insulation peak frequencies aligning closely with those of the single-membrane configurations. This study introduces an innovative performance tuning mechanism, offering valuable insights into the design of advanced tunable MAMs.