Computational methods and experimental measurements of scattered ultrasonics transient fields

Abstract

The aim of this study is to find the transient acoustic field scattered by a target with a known dimension and geometry. The target is a rigid reflector immersed in an isotropic, homogeneous, and lossless fluid. For that purpose, the presented model takes into account not only the impulse response of the insonified medium, but also that of all the elements which constitute the electroacoustic line. The main elements of the latter are a transmitter-receiver system and an ultrasonic probe modeled by its electroacoustic and acoustoelectric impulse responses. In the hypothesis of a linear, invariant, and causal measurement line, the detected pressure is expressed in the form of a time convolution between the impulse response of all the elements which compose the electroacoustic line and the impulse response of the medium. This last depends on the geometry of transducer, target, their relative position, and the propagation medium. A signal processing method of the experimental data is developed in order to evaluate the global impulse response system. The results of this process will then be used to obtain, by simulation, the effective pressure signal. Some experimental results are presented to show the good agreement with the theoretical model proposed.