Shallow-water transmission loss prediction using the Biot sediment model

Experimental data and predicted propagation loss from three shallow-water test sites with highly varied sediments are compared for frequencies from 25 to 800 Hz. The predicted loss was obtained using normal-mode and adiabatic normal-mode models with the sediment absorption calculated using the theory of Biot. The theory predicted a linear variation of absorption with frequency for a site off Corpus Christi, Texas, having a mud bottom (the mean grain size was 6.37 phi). The absorption was predicted to vary as frequency raised to the 1.76 power for a site off Daytona Beach, Florida having a medium-to-coarse sand bottom (the mean grain size was 0.85 phi). Range-independent propagation was assumed for the sites just noted and the agreement between measured and predicted loss was good for frequencies from 100 to 600 Hz. Range-dependent conditions existed for the third site, off the coast of Nova Scotia, where the sound-speed profile, bottom sediments, and depth varied with range. Good agreement was obtained between measured, 1/3-octave transmission loss values and predicted values for frequencies of 25, 80, and 250 Hz.