Broadband acoustic metamaterials with electro-magnetically controlled properties

The proposed class of acoustic metamaterials utilizes clouds of electrically charged nano or micro particles exposed to an external magnetic field. The particles are also elastically supported or embedded into elastically compliant medium in a way that the designed structure exhibits two resonances: mechanical spring-mass resonance and electro-magnetic cyclotron resonance. It is shown that if the cyclotron frequency is greater than the mechanical resonance frequency, the designed structure could be highly attenuate (40-60 dB) for vibration and sound waves in a very broad frequency range covering low and very low frequencies. The approach opens up wide range of opportunities for design of adaptive acoustic metamaterials by controlling magnetic field and/or electrical charges.