Michel De Billy
G. P. S. Univ. Paris VI and VII, Tour 23, 2 Place Jussieu, 75251 Paris Cedex 05, France
As it was observed, it is shown that for particular frequencies, a square cross section normally insonified gives rise to resonance phenomenon. This is illustrated by using two different acoustic approaches: a dynamic visualization of the pressure scattered by a square bar and a measurement of the reradiated acoustic pressure in a plane normally oriented to the axis of a square rod. Different structures of the angular patterns are observed according to the nature of the excited guided mode. The experiments were performed on specimens of different materials such that the value of the product of the frequency times the width of the rod is less than 28 MHz mm. A theoretical approach based on the Fraser's work [W. B. Fraser, Int. J. Solids Structures 5, 379--397 (1969)] will be proposed.