| Popis: |
In recent years, acoustic black holes (ABHs) have been shown very effective to suppress radiation. However, below the cut-on frequency, the waves cannot be trapped into the ABH. In this paper, locally resonant metamaterials are introduced to the ABH plate to improve the low-frequency performance. The suggested material is called MMABH. The total mass of resonators is kept the same to the one when fabricating the ABH, such that the lightweight feature still remains valid for the MMABH. Using the Gaussian expansion component mode synthesis (GECMS) method, the band gap and the coincidences between the MMABH and the air are first characterized, together with the paramagnetic studies of the plate thickness and lattice constant. In what follows, the vibration field of the MMABH is recovered, showing that whole-band reduction can be achieved. The sound pressure, power and radiation efficiency are next characterized via a discretized radiation model. Likewise, the radiated power is substantially mitigated in the whole frequency range being considered. Finally, the implementation of non-negative intensity (NNI) shows that the sound reduction not only associates with the outstanding damping capabilities of the resonators and the ABH, but also involves the wave slowdown phenomenon that breaks the coupling with air. |
