Experimental research on a sound insulation structure based on embedded Helmholtz resonators

The structures containing Helmholtz resonators (HRs) have been demonstrated to be one of the metamaterials with negative parameters. Due to its local resonance, the one- and two-dimensional structures were indicated having local resonant forbidden band, which are possible ways to attenuate low-frequency acoustic waves and oscillations. At the resonant frequency, the incident acoustic energy is almost localized around the resonator, when a local resonant gap (LRG) appears at the end of the structure. Since the existence of LRG is only associated with the properties of single resonator, a wide band gap can be produced using periodically arrayed HRs with gradually changed parameters. In this structure, neighbor forbidden gaps are overlapped. A sound insulation device is designed and implemented in this paper based on embedded Helmholtz resonators (HRs). This structure is feasible to insulate acoustic waves transmitting above it. Numerical and experimental results both show that a low-frequency wideband insulation area can be formed by circularly arrayed HRs. The working band can be adjusted by changing the resonant frequency of the HRs in each layer.