Abstract: The invention provides a system and method for monitoring the dynamics of particle motion in a liquid-solid media including the rate of settling of particles, the identification of unsettled particle clouds, and the identification and control of the bed level of settled particles in a slurry within a settler. The system includes an ultrasound transducer and a receiver for detecting echoes from particles in the slurry. The echoes are processed to determine the bed level of the settled particles, the position of unsettled particle clouds, and the rate of settling of the particle clouds.