Time-scale analysis of acoustic scattering by elastic spherical shells for impulse sources. Analyse temps-echelle de la diffusion acoustique par des coques spheriques elastiques en regime impusionnel.
Résumé
Time-frequency methods, such smoothed Wigner-Ville transforms, have already been used in studies of the possibility of characterizing scatterers of simple geometric shape. We present here results obtained with the help of a time-and-scale method, the so-called wavelet transform. This transform is used here to analyze results from a scattering experiment on spherical elastic shells, in water. The results obtained are as yet preliminary and semi-quantitative. They indicate however convincingly that certain physical quantities such as type of waves, group velocity, and dispersion laws can be estimated with the help of wavelet methods.
Mots clés
- spherical elastic shells
- dilation parameter
- asymptotic method
- stationary phase point
- amplitude modulation laws
- frequency modulation laws
- wave front
- group velocity
- Wigner-Ville transform
- impulse source
- acoustic scattering
- squeleton
- ridge
- time-frequency method
- complex wavelet transform
- Time-scale analysis
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