Optimization of time-reversal acoustic focusing

Abstract

Time-reversal acoustic (TRA) focusing systems are typically based on an acoustical resonator (a cavity) in which the multiple reflections of a bouncing acoustic pulse act as a virtual phased array. The efficiency of the TRA focusing system depends on the spectral and temporal parameters of the focused pulse and parameters of the resonator, such as its shape, size, and the relative position of its transducers. The acoustical properties of the resonator material, parameters of the sonicated medium, and the coupling of the TRA resonator and sonicated medium may also affect efficiency. Optimization of such a multiparametric system is a complex problem which is nearly impossible to achieve empirically without an adequate theoretical model. A theoretical model for predicting the efficacy of TRA focusing has been developed and experiments testing theoretical predictions were conducted. The experiments were conducted using a 10-channel TRA system developed in Artann with several broadband resonators in the frequency band of 0.1–2 MHz. The measured dependences of the focused signal on the acoustic pulse spectrum and duration, coupling of the resonator with the sonication medium, and the modes of TRA signal formation (analog or binary) confirmed theoretical predictions. [Work supported by NIH.]