A device for generating acoustic pulses by driving suddenly into a body lowered in a well a piston having a face in contact with the liquid contained in the well and adapted for sliding inside said body. The device comprises a valve securely fixed to the piston, a second piston and a hydraulic system disposed completely in the body and comprising principally a pump, electro-valves, an equalizing cylinder, a low pressure reservoir and supply circuits, for moving the valve and the piston to a set position and for immobilizing it intermittently.