The short pulse method of isolation and identification of resonances: Comparison with a quasiharmonic method and application to axisymmetrical scatterers

Several experimental methods using quasiharmonic insonification lead to a direct verification of the resonance scattering theory. They provide, for elastic cylindrical targets, the resonance frequencies and the mode number of each of them. Pulsed techniques already existing only allowed the resonance frequency determination. Recently, a short pulse method of isolation and identification of resonances (short pulse MIIR) has been initiated. It completes previous works and allows a complete comparison with theoretical and quasiharmonic experimental results. This method consists in digitizing the time signals that characterize the scattering from an elastic target insonified by a short pulse for different angular positions of the receiving transducer. For each acquired signal a resonance spectrum is obtained after a spectral amplitude analysis. From these data, computer processing allows the plotting of identification patterns and by the same way the knowledge of the mode of vibration at a given resonance frequency. Even if this method is not restricted to cylindrical scatterers, this paper presents the identification of resonances by means of the short pulse MIIR of targets as cylinders, shells and water-filled shells and cavities. The accuracy and the possibility for separating overlapping resonances are also discussed.