Much of modern electronic engineering terminology originates from acoustics: harmonic excitations, octaves, horn antennas, and so on. Sound is also a tool for a variety of sensing techniques, including geological and medical imaging, airborne and underwater sonar, and non-destructive testing of metallic parts. The same “unit-cell” control that enables metamaterials to interact with radio waves and light in novel ways can be used to control the acoustic response of materials.
Given the broad scope of acoustic devices, we anticipate acoustic metamaterials will be used in many situations, ranging from familiar settings of home audio systems to more exotic roles in ultra-slim, efficient, sound-proofing coatings and vibration dampers. At sound frequencies above human hearing and using smaller unit-cells, acoustic metamaterials can be used in medical ultrasonography, millimeter-precision gesture readers for human-machine interfaces, and near-range sonars for small aircraft. At even smaller scales, acoustic metamaterials can be used to control thermal conductivity, showing promise as thermal insulators and efficient heat exchangers.