A device for sifting, sorting, screening, filtering or sizing dry solid substances of solid substances in liquids has a sifting surface arranged in a sifting frame and an ultrasonic transducer (10) associated thereto, through which vibrations may be transmitted to the sifting surface (18). At least one resonator (14) arranged on the sifting surface (18) is associated to the ultrasonic transducer (10), is tuned to the resonance of the ultrasonic transducer and may be made to vibrate, in particular with bending vibrations, by the ultrasonic transducer. The resonator (14), which in one embodiment is arranged at the middle of the sifting surface (18), is provided with resonance-transmitting, finger-like elements (14) which radially extend away from the resonator (14) over the sifting surface (18) and act as rod resonators.