Architected Lattices for Simultaneous Broadband Attenuation of Airborne Sound and Mechanical Vibrations in All Directions

Since their inception, more than two decades ago, phononic crystals and metamaterials have led to advanced materials with exceptional acoustic and elastic characteristics, such as negative effective mass and stiffness. In these materials, the dispersion properties and the energy transfer are controlled by selecting the geometry of the lattices and their constitutive material properties. Most designs, however, only affect one mode of energy propagation, transmitted either as acoustic airborne sound or as elastic structural vibrations. Furthermore, they are divided based on the main driving physics into subcategories that entail either Bragg scattering or local resonances, but rarely both. Such separation based on host medium or driving physics, hinders the realization of universal multi-functional metamaterials. Here, we present a design methodology to attenuate both acoustic and elastic waves simultaneously in all polarizations. Our material harnesses both scattering and resonances within the same design. We experimentally realize a three-dimensional load-bearing architected lattice composed of a single material. Our metamaterials respond in a broadband frequency range in all directions and polarizations for both airborne sound and elastic vibrations simultaneously, covering more than 60% of audible frequencies. [Link]