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
Time-scale analysis
complex wavelet transform
time-frequency method
ridge
squeleton
acoustic scattering
impulse source
spherical elastic shells
Wigner-Ville transform
group velocity
wave front
frequency modulation laws
amplitude modulation laws
stationary phase point
asymptotic method
dilation parameter