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Description
Low-frequency room modes remain a major challenge in architectural acoustics, as they cannot be effectively mitigated using conventional absorbers or resonators without a significant thickness. As an alternative, acoustic metamaterials offer the possibility of achieving efficient low-frequency absorption with limited thickness. In this work, a numerical methodology for the design and optimisation of a spiral metasurface aimed at room mode control is presented. A finite element model of a rectangular enclosure is implemented in COMSOL Multiphysics and adjusted using measurements. Based on the modal characteristics of the room, a spiral labyrinth structure is designed and tuned to target a specific low-frequency mode. Analytical and numerical simulations are conducted to evaluate the absorption performance of the spiral metasurface and to optimise both its internal geometry and its spatial distribution within the enclosure. The selected geometries are then 3D printed and their performance is assessed experimentally using an impedance tube. The good agreement between numerical simulations and measurements exhibits the potential of this approach as a tool for acoustic metamaterial design for room-mode control. The observed amplitude reduction of the selected room mode shows that metasurfaces based on labyrinth structures are an effective and scalable solution for low-frequency modal control in enclosures, overcoming the limitationsof traditional absorptive materials.