Abstract: Comingled particles, such as nut meats and shell fragments, are segregated by directing the particles one after the other onto a sounding plate, from which they deflect into a rebound trajectory. Each particle upon striking the plate imparts ultrasonic vibrations to the plate, and these vibrations are converted by a transducer into an electrical input signal that oscillates at the frequency of the vibrations and undergoes corresponding changes in amplitude. After amplifying the input signal and filtering low frequency signals from it, a comparator converts those original oscillations which exceed a predetermined threshold amplitude into voltage pulses that are counted in a counter. If the count exceeds a minimum set into the counter, the counter produces a signal itself. This signal initiates an output signal of predetermined duration, which after undergoing a delay, operates an air valve that is connected with an air nozzle located along the rebound trajectory.