Abstract: Process and apparatus for treating material by applying non-sinusoidal vibrations. In apparatus for separating solids from the liquid phase of a dispersion, non-sinusoidal vibration is applied by vibrating at least a portion of a wall of a receptacle for the dispersion or by a vibrating plate, a pair of vibrating plates or a hollow body in the receptacle. In a roller mill for crushing material one of the rollers is vibrated axially relative to the other. In a juice press a vibrating plate is provided at the bottom of the press cylinder. In a jaw crusher, one of the jaws is vibrated in a direction parallel to the face of the jaw. In a ball mill comprising a cylinder rotating on a horizontal axis, the cylinder is vibrated in an axial direction. Non-sinusoidal vibration is produced by a hydraulic servomotor fed with pulses of hydraulic pressure fluid by a rotary control valve.