Soft Acoustic Metamaterials

摘要

Resonance phenomena occur with all types of vibrations or waves and may play a part in spectacular events, such as the collapse of structures-for example, the fall of the Broughton suspension bridge near Manchester in 1831 (1). Indeed, the oscillations of a structure submitted to harmonic excitation reaches its maximum amplitude at the resonance frequency ω_0 of the system. At low driving frequencies (ω ＜ ω_0), its response is in phase with the forcing but becomes out of phase just beyond (ω_0 ＜ ω). Such an out-of-phase response has been exploited with "locally resonant materials" . The proposed strategy is to embed a large enough collection of identical mechanical resonators in a passive structure to control wave propagation. These features are used to reach unusual macroscopic behaviors such as ultradamping of noise or negative refraction for imaging.