Acoustic metamaterials and metasurfaces: a transformative approach for phononic insulators and energy harvesting

First, we will provide some recent advances on low-frequency phononic and acoustic insulators based on metasurfaces. We will introduce a new concept of acoustic absorption based on the coiling-up space design which exhibits extreme acoustic properties. A new acoustic absorber operating at 125Hz with deep-subwavelength thickness (similar to lambda/230) acting as an "acoustic sink" is designed and its functionalities are discussed. Second, as we are dealing with how to reduce or to absorb low-frequency sound/noise, we will explore a novel idea on the use in a positive manner these noises as a source of energy. We theoretically and numerically show the properties of a novel acoustic energy harvester resulting from the confinement and conversion of low-frequency acoustic/noise disturbances to electrical energy. We indeed present preliminary results showing a metamaterial structure producing an electrical power density of 0.54 mu w/cm(3) for one confined frequency, which presents a very good value compared the others acoustic energy harvesting approaches.