Localization of ultrasound in 2D phononic crystal with randomly oriented asymmetric scatterers

A phononic crystal of aluminum rods with an asymmetric cross section in water is used for the study of Anderson localization of sound. Due to asymmetry, these scatterers may be arranged in three different configurations: a periodic 2D structure, a random structure with 2D disorder, and a random structure with 1D disorder. The last configuration where the rods are equally oriented within the columns and disoriented along the rows is fabricated for the experimental study of 1D Anderson localization in the 2D random system. An exponentially weakening transmission of the ultrasound is demonstrated for the waves propagating along the direction of disorder. In the perpendicular direction where the scatterers are ordered, sound propagates as an extended (delocalized) wave. The localization length is controlled by the degree of disorder. For weak disorder, when orientations of the rods weakly fluctuate around a given direction, Thouless's theoretical prediction for the scaling of the Lyapunov exponent with disorder is experimentally observed for a mode within the transmission band. For the sound mode close to the band edge, anomalous scaling is confirmed.

Automated summary

A phononic crystal of aluminum rods with asymmetric cross section in water is used to study Anderson localization of sound. Different configurations of scatterers are explored, showing weakened transmission in the direction of disorder and extended wave propagation in the ordered direction. The localization length is controlled by the degree of disorder, with experimental observations confirming theoretical predictions for particular modes.