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.