A new method to determine the elastic resonance characteristics (the resonance frequency and the associated width) of acoustic targets imbedded in a fluid medium is presented. The basic idea is that the resonant pressure exhibits a Breit-Wigner spectral form as the Resonance Scattering Theory (R.S.T.) has previously shown. This typical resonant shape obeys a complex expression whose presentation in the complex pressure plane (the Argand diagram of the resonance) has useful mathematical singularities. The theoretical characteristics of an elastic resonance can be obtained using only the geometrical properties of the Breit-Wigner form. Furthermore, this determination does not need the equation of the background to be invoked. From the experimental point of view, the same approach is possible. However, the sampling and the time limited recording of a temporal signal modify in a non linear way the expected resonant spectrum. Hence, the temporal resonance duration alters the aspect of the Breit-Wigner resonant form. As a result, because of the presence of this supplementary factor, the experimental determination of the resonance characteristics becomes more complicated. Nevertheless, a procedure is proposed and the experimental results agree with the theoretical ones. [References: 8]
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