Abstract: A method for determining the concentration of a large particle component in a multi-component system. The method requires first separating and concentrating the large particle component of the system by acoustic means and then measuring an acoustical parameter of the separated large particle component. The invention also provides for an apparatus for determining the concentration of large particles in a multi-component fluid system. The apparatus is comprised of an acoustic standing wave resonator, at least one acoustic standing wave generating source, electronic circuitry for actuating, controlling and processing the acoustic standing wave generating source and means for measuring at least one parameter of the multi-component system after the large particles have been concentrated and aggregated by the generated standing wave(s).