Two types of locally resonant sonic metamaterials (LRSM) that functions in sub-kHz region are fabricated and experimentally characterized. The membrane-type LRSM, which consists of a central rigid mass attached on a tightened piece of circular rubber membrane, shows two transmission peaks with a dip in between. Its behavior can be explained by the simple spring-mass model and the eigenmode resonance of circular membrane. We further utilize the laser Doppler vibrometer (LDV) to actually measure the local displacement on the sample point by point. The results lend good support to the understanding to the underlying physical picture. Another type of LRSM which features 4 Helmholtz resonators (HRs) with orifices perpendicular to their respective neighbors is also fabricated and experimental...[ Read more ]

Two types of locally resonant sonic metamaterials (LRSM) that functions in sub-kHz region are fabricated and experimentally characterized. The membrane-type LRSM, which consists of a central rigid mass attached on a tightened piece of circular rubber membrane, shows two transmission peaks with a dip in between. Its behavior can be explained by the simple spring-mass model and the eigenmode resonance of circular membrane. We further utilize the laser Doppler vibrometer (LDV) to actually measure the local displacement on the sample point by point. The results lend good support to the understanding to the underlying physical picture. Another type of LRSM which features 4 Helmholtz resonators (HRs) with orifices perpendicular to their respective neighbors is also fabricated and experimentally characterized. It is qualitatively shown in the thesis that the mechanical resonance and the coupling between resonance and background sound wave are accounted for its special transmission property. Moreover, two different sets of results on the coupling between the two types of LRSMs are also reported in this thesis.