Publication
Control of sound with active metamaterials presents several apparent advantages over passive approaches such as extended bandwidth of control, tunability of the technique, new acoustic properties not achievable with passive materials, and often a more compact form factor. However, the loudspeakers and other membrane-based electroacoustic transducers, which are typically used as the building blocks for active metamaterials, have limited authority on the control bandwidth due to their resonant nature. This work discusses a plasma-based acoustic metalayer that fundamentally differs from conventional transducers. The acoustic field is directly controlled through the interaction of the air particles with a layer of ionized air, which is produced in the metamaterial. This transduction principle allows reacting faster than membranebased interfaces to an input acoustic signal and considerably increases the bandwidth of control. We demonstrate the broadband control of acoustic impedance, realizing a wide spectrum of acoustic properties, from a strongly reflecting interface to a perfect sound absorber. The plasmabased acoustic metalayer presents a promising concept for the research on acoustic metamaterials as the phase of the wave can be also controlled in a broadband manner.