The presence of gas bubbles in the bottom of shallow marine and freshwater reservoirs significantly reduces the speed of sound. The amount of gas in the bottom depends on microbiological activity, and therefore pollution level is an indicator of the ecological balance. It is proposed to control the level of bottom contamination by measuring sound reflection coefficient or measuring the input bottom impedance. The frequency-angular reflection coefficient dependences and frequency dependences of the input bottom impedance are calculated. It is shown that the principal point of the results correct interpretation is the inclusion of intergranular friction and sound velocity dispersion in marine sediments.
marine sediments, phase-velocity dispersion, intergranular friction, gas-saturated sediments, rate of decay, reflection coefficient, bottom impedance
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