New waveguide method for studying water-saturated sediment sound speed dispersion at low frequencies
Abstract
This research investigates a new technique to measure the sound speed in
water-saturated sediment at low frequencies (under 2 kHz). Due to the difficulty in
acquiring low frequency data, dominant models for predicting sediment sound
speed dispersion, such as the Biot model, have not been thoroughly experimentally
verified in the low frequency region. Future experiments will collect data to compare
against this elusive region of the model, but for now we chose an idealized
sediment whose portion of the predicted dispersion curve in our frequency range
had held up well to experimental verification in the past. We used the resonance
measurements from both an aluminum and glass waveguide with packets of
idealized sediment strung along their axes to indirectly measure the water-saturated
sediment sound speed. We tried both a Matlab analysis combining several
theoretical models and also numerical modeling with COMSOL to analyze the data.
Although there are still some problems with the data analysis, it has the potential to
be a valid and powerful new technique to evaluate the low frequency region of the
Biot model.