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Pré-Publication, Document De Travail (Preprint/Prepublication) Année : 2023

Gaussian derivative wavelet propagation in a single scattering bubbly water beyond resonance frequency

Yves Le Gonidec

Résumé

Acoustic pulses transmitted across air bubbles in water are usually analyzed in the ν frequency domain to determine attenuation and phase velocity for comparison with effective models. In the present work, acoustic experiments performed beyond the bubble resonance frequency highlight an attenuation approximated to a(ν/ν0)^(-y) with y>0 and ν0 the wavelet source peak frequency, a significant shape variability of the waveform with the propagation distance x<0.74m, and 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. The phase spectrum is shifted by πγ_x/2 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. With the assumption ayx<0.15, the range of applicability may be extended to the ocean water column around gas seep sites with potential interests in underwater communication.
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Dates et versions

hal-04031534 , version 1 (16-03-2023)
hal-04031534 , version 2 (03-07-2023)

Identifiants

  • HAL Id : hal-04031534 , version 2

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Yves Le Gonidec. Gaussian derivative wavelet propagation in a single scattering bubbly water beyond resonance frequency. 2023. ⟨hal-04031534v2⟩
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