A frequency domain inversion method applied to propagation models in unconsolidated granular materials

Area of Science:

• Geophysics
• Acoustics
• Material Science

Background:

• Accurate characterization of sediment physical properties is crucial for understanding wave propagation phenomena.
• Existing models for sediment acoustics often simplify or neglect complex viscoelastic behaviors, including absorption and dispersion.

Purpose of the Study:

• To develop and validate a general viscoelastic model for characterizing sediment physical parameters.
• To investigate wave propagation, absorption, and dispersion within sediments using transmission and reflection experiments.

Main Methods:

• Experimental setup involving a water-filled tank with a Plexiglas-sediment-Plexiglas configuration.
• Utilized transducers and a pulser-receiver for acoustic transmission and reflection measurements.
• Employed a rational transfer function to model the viscoelastic modulus and a maximum likelihood estimator for parameter estimation in the frequency domain.

Main Results:

• The proposed general viscoelastic model successfully accounts for wave absorption and dispersion in sediments.
• Comparisons with constant Q viscoelastic and Biot models demonstrate the enhanced capability of the new model.
• The frequency-domain maximum likelihood estimator effectively estimated the model parameters.

Conclusions:

• The developed viscoelastic model provides a more comprehensive approach to determining sediment physical properties.
• This method offers improved accuracy in characterizing acoustic wave interactions with sediments, considering energy losses.
• The findings have implications for geophysical exploration, underwater acoustics, and sediment transport studies.