Acoustic metamaterial

Acoustic metamaterials, sometimes referred to as sonic or phononic crystals, are architected materials designed to manipulate sound waves or phonons in gases, liquids, and solids. By tailoring effective parameters such as bulk modulus (β), density (ρ), and in some cases chirality, they can be engineered to transmit, trap, or attenuate waves at selected frequencies, functioning as acoustic resonators when local resonances dominate. Within the broader field of mechanical metamaterials, acoustic metamaterials represent the dynamic branch where wave control is the primary goal. They have been applied to model large-scale phenomena such as seismic waves and earthquake mitigation, as well as small-scale phenomena such as phonon behavior in crystals through band-gap engineering. This band-gap behavior mirrors the electronic band gaps in solids, enabling analogies between acoustic and quantum systems and supporting research in optomechanics and quantum technologies. In mechanics, acoustic metamaterials are particularly relevant for designing structures that mitigate vibrations, shield against blasts, or manipulate wave propagation in civil and aerospace systems.