Abstract
We present an acoustic metamaterial (AMM) consisting of a dumbbell-shaped split hollow sphere (DSSHS). Transmission results of experiments and simulations both presented a transmitted dip at the resonant frequency of AMM, which demonstrated its negative modulus property. As the two split holes in the DSSHS had strong coupling effects for the acoustic medium in the local region, the dip could be simply manipulated by tuning the distance between the split holes. When the distance was large enough, the mutual inductance tended to disappear, and a weak interaction existed in the structure. According to the property of weak interaction, a multiband AMM and a broadband AMM with a negative modulus could be achieved by arraying DSSHS clusters with different distances. Furthermore, mutual inductance and coupling in DSSHS reinforced the local resonance, and this kind of cell could be used to design the acoustic metasurface to abnormally control the refractive waves.
Highlights
The proposal of metamaterials [1,2] accelerates the development of abnormal manipulations of waves
The dumbbell-shaped split hollow sphere (DSSHS) was located in an acoustic waveguide tube with a periodic boundary, which meant that the DSSHS acoustic metamaterial (AMM) was designed by the periodic
Presented a transmission dip, as shown in Figure 2a, which was similar with the single SHS AMMs
Summary
The proposal of metamaterials [1,2] accelerates the development of abnormal manipulations of waves. As the concept of local resonance is introduced into the acoustic field [12], acoustic metamaterials (AMMs) (bulk material) or metasurfaces [13] (with subwavelength thickness) present similar properties for acoustic waves as the EM counterparts such as double negative parameters, flat focusing, subwavelength imaging, cloaking, abnormal reflection and refraction, phase engineering, total sound absorption, topology inspired characteristics [14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29], damping ratio enhancement, the band gaps of vibration, and so on [30,31,32,33]. Yang et al used membranes with different weights to achieve broadband sound attenuation [36] Another method is coupling local resonance with Bragg band gaps [40,41]. We will introduce another method of resonant coupling between the unit cells to achieve a broadband AMM with a dumbbell-shaped split hollow sphere (DSSHS) structure.
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