Abstract: This vibration generator intended more particularly for impressing a vibratory motion to vibrating apparatus such as handling circuits and treatment stations for loose materials and products comprises an excitation eccentric rotatably driven from a motor and adapted, during at least one fraction of its stroke, to co-act with a roller lined with resilient material mounted in a fixed position on the apparatus, the axis of rotation of this eccentric being coupled to means controlling its movement substantially in the direction towards the apparatus. Thus, the amplitude and frequency of the vibratory motion can be modified while in operation, either manually or automatically.