INTERFERENCE ASPECT OF THE INTERACTION BE TWEEN 2 ELASTIC TUBES - IMPULSIVE AND QUASI-HARMONIC STUDIES

The acoustic scattering from a target composed by two elastic cylindri cal shells immersed in water is experimentally studied. Two methods ar e used: the first is the impulsive one, the second the quasi-harmonic one. The shells and the transducer emitter are in an eclipsed configur ation. The impulsive method allows us to obtain, on the first hand, th e resonance spectrum, and on the second hand, the paths of the waves i nvolved in the scattering. The quasi-harmonic method shows that the sc attering involves an interferential phenomenon related to radiation an d reradiation by the two shells. Consequently, the acoustic scattering results from two complementary phenomenon: the resonant one and the i nterferential one. The last aspect is experimentally shown by the anal ysis of the different regimes obtained in the quasi-harmonic backscatt ering and by the study of the angular diagrams in the reemission regim e. A theoritical study gives angular diagrams which agree very well wi th the experimental ones; it clearly shows the interferential phenomen on.