Acoustic metamaterials have been undoubtedly an important research theme in recent years. Acoustic metamaterials are artificially-structured materials that can manipulate and control sound waves in ways that are not possible in conventional materials. It is an exciting and rapidly-expanding topic in the field of physical acoustics that, for more than 20 years now, has continued to give rise to exotic wave phenomena, such as acoustic cloaking, perfect absorbers, sound focusing based on gradient index lenses, acoustic topological systems, non-reciprocal propagation, PT-symmetric sound manipulation or waveguides immune to backscattering and others. In addition, recently, nonlinear acoustic metamaterials have been receiving increasing attention through studies, e.g., on acoustic diodes, bifurcation-based acoustic switching and rectification, nonlinear acoustic lenses, and acoustic solitons.

This Special Issue will reveal both fundamental wave aspects of acoustic metamaterials as well as their practical perspectives. It provides a unique forum for discussion and presentation of recent advances. Scientists working in this broad field are invited to present their work in this Special Issue.