Acoustic scattering by elastic bodies is usually analyzed in terms of resonances, the frequency, width, and order of which should be determined. In this paper, a simple approach based on a frequency derivative of the scattered pressure is proposed for resonance order identification on bodies of arbitrary shape. The method is applied to the acoustic scattering of a plane wave by a spherical shell for validation and by a cylindrical shell bounded by hemispherical end caps. In both cases, theAandS0wave resonances are identified.