Time reversal acoustic focusing with liquid-filled reverberator

Abstract

The use of solid acoustic reverberators for temporal and spatial focusing of acoustic energy based on time reversal acoustic (TRA) principle was described in the literature. We experimentally and theoretically demonstrated that the liquid-filled TRA reverberators can also efficiently focus acoustic energy and compared the advantages of solid and water-filled reververators. A theoretical model was developed to explore the factors defining the efficiency of TRA focusing, providing the design constraint for the water-filled reververators. The model allows evaluation of the spatial and temporal characteristics of TRA focused acoustic field formed as a result of numerous reflections of ultrasound within the reverberator. The TRA focused field structure, its dependence on the shape and size of the resonator, ultrasound frequency, and attenuation were investigated for the standard and binary modes of TRA focusing. The experiments with custom built liquid-filled acoustic resonators confirmed the predictions of a developed theory, including sharpening of the focal area and increasing of the focal intensity in a binary mode of TRA focusing. The conducted research supports suggestion that such liquid-filled reverberators can be considered as a base for a miniature limited range ablation devices for biomedical applications.