Extension du modèle de Freedman de formation des échos au cas transitoire

Abstract
This paper presents an extension of a model presented by the same authors in the previous CFA [1]. The model allows fast computations of the acoustical impulse-response of the problem of the radiation of ultrasonic pulses by realistic transducers, their scattering by immersed targets and their reception. In the previous version, the model was restricted to the case of small targets centered on the transducer axis. Here, it is shown that a more general formula can be derived allowing the computation of the echo-responses from targets not necessarely centered on axis which can be of arbitrary size. It is shown that the present model may be considered as an extension to the transient case of the well-known Freedman's model which derived from a CW theory. Basically, the idea is to restrict the computation to the contributions arising from the only parts of the target where interferences are constructive.