Current research in acoustic materials and metamaterials is being conducted within our Branch with the goal of constructing novel devices for use in aqueous, air, and elastic environments. This work seeks to both understand and develop the underlying physics of acoustic and elastic solid wave propagation in engineered and/or patterned materials in order to determine the physical properties and geometries of constituent components required to create a desired behavior of the bulk material. Device designs and materials based on theoretical and numerical calculations of performance can be fabricated and experimentally tested in world class facilities. This work also includes investigations into rheological, piezo, and composite materials as possible media to provide control over the bulk acoustic properties of a given material. Additional work involves the study of phonons in nanoscale materials, as well as novel uses of MEMS devices at NRL's Nanoscience Institute. Opportunities exist to complete original theoretical/numerical/experimental research backed up by the Nanoscience Institute, four acoustic tank facilities, aero-acoustic facilities, and a new Laboratory for Additive Manufacturing. In addition, numerical analysis is supported by the Laboratory’s large cluster of high-performance computers. This combination of facilities provides an excellent backdrop to pursue exciting new research opportunities in acoustic wave propagation, acoustic materials research, metamaterials research, and the physics of phononic interactions in solid materials.