Recent advances in acoustic metamaterials have overcome narrow‐band limitations, allowing for optimal tuning of key functions such as sound absorption and diffusion. However, most existing designs focus on single functions, leaving a gap in multi‐functional solutions that can address complex acoustic requirements. To fill this gap, a Dual‐Function Passive Acoustic Metamaterial (DFPAM) is proposed that effectively balances absorption and diffusion within the same structure by leveraging principles of causality and passivity. The DFPAM achieves high broadband sound absorption (〈α〉 ≈ 0.85) and diffusion (〈δ〉 ≈ 0.8), covering more than one octave in each configuration. With a compact thickness of only 12 cm, nearly half that of traditional treatments, this design uses just a fraction of the available space (1/3 for absorption, 2/3 for diffusion) while maximizing performance. This novel approach not only optimizes sound control but also provides a highly space‐efficient solution. The DFPAM offers transformative possibilities for room acoustics and can be adapted to diverse environments, including building and aerospace applications, where multi‐functional acoustic solutions are in increasing demand.

Sound diffusion refers to the ability of a surface to evenly scatter sound energy in both time and space. However, omni-directional radiation of sound, or perfect diffusion, can be impractical or difficult to reach under traditional means. This is due to the considerable size required, and the lack of tunability, of typical quarter-wavelength scattering strategies necessary for producing the required complexity of the surface acoustic impedance. As such, it can be a challenge to design sound diffusing structures that can display near perfect diffusion performance within slim dimensions. In this work, we propose a method for obtaining quasi-perfect and broadband sound diffusion coefficients using deep-subwavelength acoustic diffusers, i.e., metadiffusers. The relation among the geometry of the metasurface, the bandwidth, and the diffusion performance is analytically and numerically studied. For moderate bandwidths, around 1/3 of an octave, the method results in nearly perfect sound diffusion, while for a bandwidth of 2.5 octaves, a normalized diffusion coefficient of 0.8 was obtained using panels 1/30th thinner than traditional phase-grating designs. The ratio between the wavelength and the size of the unit cell was identified as a limitation of the performance. This work demonstrates the versatility and effectiveness of metadiffusers to generate diffuse reflections outperforming those of classical sound diffusers.

Self-organized Turing patterns, arising from the dynamic interplay of reaction and diffusion processes, are instrumental in modeling natural morphogenesis and deciphering the biological functions of diverse structures. These patterns exhibit complex spatial arrangements that can be analyzed through the lens of statistical mechanics, particularly in relation to hyperuniformity-a state characterized by suppressed long-range density fluctuations. Despite this, the connection between Turing patterns and hyperuniformity remains relatively unexplored. In this study, we examine the spatial distribution of generic Gray-Scott patterns and Arabidopsis thaliana trichome patterns, linking their morphogenesis to disordered hyperuniform patterns. Our findings demonstrate that hyperuniformity emerges in Turing patterns as a solution to a reaction-diffusion equation system, reaching its apex in a specific region of the Gray-Scott phase space marked by dotlike spatial patterns. Mapping the hyperuniformity classes in this region reveals patterns with class III hyperuniformity surrounding special class I solutions. By extending this framework to biological systems currently under investigation for mechanosignalling triggrered immunity, we show that A. thaliana trichomes form class III disordered hyperuniform systems. Such exotic organization, as described by Turing patterning, has a strong potential to influence mechanically triggered immune response, offering novel insights into plant mechanoperception.

Most simulations involving metamaterials often require complex physics to be solved through refined meshing grids. However, it can prove challenging to simulate the effect of local physical conditions created by said metamaterials into much wider computing sceneries due to the increased meshing load. We thus present in this work a framework for simulating complex structures with detailed geometries, such as metamaterials, into large Finite-Difference Time-Domain (FDTD) computing environments by reducing them to their equivalent surface impedance represented by a parallel-series RLC circuit. This reduction helps to simplify the physics involved as well as drastically reducing the meshing load of the model and the implicit calculation time. Here, an emphasis is made on scattering comparisons between an acoustic metamaterial and its equivalent surface impedance through analytical and numerical methods. Additionally, the problem of fitting RLC parameters to complex impedance data obtained from transfer matrix models is herein solved using a novel approach based on zero crossings of admittance phase derivatives. Despite the simplification process, the proposed framework achieves good overall results with respect to the original acoustic scatterer while ensuring relatively short simulation times over a vast range of frequencies.