Overhauling Sound Diffusion in Auditoria Using Deep-Subwavelength Acoustic Metamaterials

The reducedamount of space available in critical listening environments, such as orchestra pits, rehearsal rooms or even recording studios, often impairs the installation of helpful, but sizeable, acoustic treatments on their boundaries. This can be a problem as such acoustic treatments, mainly used for sound absorption and diffusion, are key for controlling the physical aspects of sound propagation in the environment. This research thus proposes to study experimentally and numerically a cutting-edge metamaterial-inspired approach designed to provide ultra-thin and adaptable alternatives to traditional acoustic treatments, with a particular focus on sound diffusion, and how these can be integrated in practical computational frameworks. These novel deep-subwavelength acoustic metamaterials, termed metadiffusers, allow for efficient sound diffusion within dimensions 1/10th to 1/20th thinner than ordinary sound diffusers. Moreover, the optimization potential of metadiffusers brings a vast panel of variable configurations depending on the situation requirements. Results presented throughout this thesis outline several of these configurations with experimental and/or numerical validations in free-field scattering scenarios as well as numerical room acoustic applications. Very good agreement is found all through between the analytical and experimental/numerical scattering and diffusion datasets, thus demonstrating the outstanding and versatile potential of metadiffusers to be applied in many critical listening environments where space is at a premium, such as orchestra pits or recording studios.