Bioinspired stochastic minimal surface metamaterials for tunable acoustic performance

• Bioinspired stochastic metamaterials are introduced as tunable alternatives to conventional acoustic foams. • Six minimal surface topologies (P + N, Neovius, FRD, IWP, Gyroid, and Primitive) were 3D printed, and their acoustic performance was evaluated experimentally and numerically within the 1–6 kHz frequency range. • Topology strongly influenced acoustic performance in stochastic foams, with designs featuring pronounced neck and cavity motifs (P + N, Neovius, FRD) achieving higher absorption. • Parametric variations demonstrated distinct design trends with decreasing the characteristic length or porosity enhanced sound absorption, whereas increasing the sample thickness shifted the effective absorption band toward lower frequencies. • Stochastic minimal surface foams provide tunable, lightweight, and high-noise control, which can be applied in aerospace, transportation, buildings, and other environments. Conventional acoustic materials limit design flexibility, and hence, in this work, we introduce bioinspired stochastic metamaterials derived from minimal surface geometries as an alternative to traditional acoustic foams. These stochastic metamaterials are equation-based and provide precise control of topology, pore size, and porosity, offering full tunability that traditional foams cannot achieve. This expanded design space enables full optimization towards specific frequency targets and weight constraints. Here, we have fabricated stochastic foams using additive manufacturing and characterised their acoustic response in the 1 kHz to 6 kHz range using a two-microphone impedance tube. We investigated six sheet/shell-based stochastic topologies (P + N, Neovius, FRD, IWP, Gyroid, and Primitive) by systematically varying the control points for generating the stochastic architecture, stochastic realizations, pore size, porosity, and thickness. We have also assessed their acoustic performance through finite element simulations based on a thermoviscous constitutive model. Topologies with pronounced neck and cavity motifs (P + N, Neovius, FRD) exhibited a superior absorption performance compared to the IWP, Gyroid, and Primitive designs. Reducing porosity or pore size improved absorption, whereas thickness tunes the operational frequency bandwidth. These findings demonstrate the potential of stochastic foams as tuneable, lightweight, and sustainable alternatives to conventional foams, enabling noise control in various applications.