Comparison of velocity and attenuation measurements to the corrected effective density fluid model for gassy sediments

Abstract

To validate the corrected effective density fluid model for gassy sediments, an acoustic experiment was undertaken to measure the velocity and attenuation over the frequency range of 8 and 120 kHz in an indoor water tank. The velocity and attenuation obtained by different estimation methods have good consistency respectively. Both of them have four distinct peaks and there is one-to-one correspondence between velocity peaks and attenuation peaks. Through numerical simulation of the acoustic characteristics attributed to the resonance of gas bubbles with different radii, the existence of small bubbles causes the velocity to decrease in the vicinity of resonance frequency of large bubbles. Five modified Gaussian functions are introduced to model the bubble size distribution inside the gassy sediment. A best bubble size distribution is obtained by inversion of the velocity and attenuation data simultaneously, and the predictions of the corrected model are broadly in good agreement with the measurements.