Gaussian derivative wavelet propagation in a single scattering bubbly water beyond resonant frequency
Résumé
Acoustic pulses transmitted across air bubbles in water are usually analyzed in the ν frequency domain to determine the attenuation coefficient and phase velocity for comparison with scattering and effective models. In the present work, acoustic experiments performed beyond the bubble resonant frequency in the single scattering regime highlight an amplitude decrease and a significant shape variability of the waveform with the propagation distance x, but also a nearly constant normalized amplitude spectrum. The amplitude spectrum can be characterized by a fractional derivative order γ x = κ γ x, with κ γ a constant defined by a numerical optimization method, and a time dilation factor δ x which effects compensate. The phase spectrum is shifted by π 2 γ x and explains the experimental waveform changes. The phase velocity can be approximated to ṽ0 /(1 − κ γ ṽ0 /4ν), where ṽ0 is similar to the sound speed in water. It is also shown that the waveform shape, quantified by γ x , is correlated to the waveform amplitude. The results highlight potential interests in underwater communication.
Domaines
Physique [physics]Origine | Fichiers produits par l'(les) auteur(s) |
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