Journal: Scientific Reports

Article Title: Acoustic rainbow trapping

doi: 10.1038/srep01728

Figure Lengend Snippet: (a) Acoustic wave trapping is the result of balanced interplay between the local groove oscillation and the mutual near field coupling among the grooves to form closed-loop circulations of “trapped sound”. When acoustic waves are trapped, the effective acoustic energy flow (black arrows) between two adjacent grooves will go opposite directions during 0- t /2 (top half) and t/ 2- t (bottom half), here t is the period of oscillation inside individual groove, thus forming an equivalent closed-loop circulation where the acoustic wave always returns to its origin, resulting in the standstill of acoustic waves. The vertical white arrows represent acoustical oscillation inside the grooves. The horizontal white arrows correspond to the diffracted evanescent waves that propagate along the interface between the metamaterial and the air. The color map is the normalized acoustic energy flow. (b) Comparison of acoustic wave trapping locations derived by 2D full wave FEM simulation on actual metamaterial geometry, the microscopic model, the quarter-wavelength resonator model, and experimental results. Microscopic model result fits well with the FEM simulation curve and experimental results, suggesting better capability in analyzing the steady acoustic wave trapping state, especially when the unit cell size is not infinite small. Experimental results start to deviate from theoretical prediction at lower frequency range, which is due to the larger wavelength and finite length of actual sample in y direction. The error bars represent s.d. among 5 repeated measurements.

Article Snippet: FEM simulations on acoustic pressure field measurement were carried by COMSOL MultiphysicsTM 4.1 with the acoustic-solid interaction multi-physics module.

Techniques: Comparison, Derivative Assay