Tunable double-layer dual-band metamaterial with negative mass density

Abstract

Due to the huge structure and low efficiency of acoustic metamaterial (AM) with local resonance, a tunable dual-band AM with nested double layer hollow tube (NDLHT) is presented here, which is achieved by adjusting the inner or outer layer tube’s lengths or diameters to modulate the frequency band with the negative mass density. In addition, an accurate resonant frequency formula for OE-CE (Open End-Close End) NDLHT was derived based on the principle of standing wave resonance. The theoretical calculated resonant frequencies exhibit in good agreement with the simulated frequencies. Thus, the structural unit can then be actively constructed in the desired response frequency range using the geometric parameters that were obtained from this theoretical formula. This type of the nested AM with negative mass density has the advantages of high space utilization, active design, programmed modelling, customized production, 3D quantitative printing and is easily combined with other structure units with negative modulus to prepare AM with double negative in the desired frequency band.