Abstract: A vibrator operated by a fluid medium under pressure for the purpose of imparting vibration to a working platform carrying the material being handled. The vibrator comprises a base, a forward stroke chamber formed by a continuous seal situated on the side of said base facing the working platform, and a striker mounted on said seal of the forward stroke chamber and adapted to interact with the working platform under the action of the fluid medium for the purpose of imparting vibration to said working platform. The vibrator also comprises a reverse stroke chamber formed by an additional continuous seal situated on the side of the striker facing the working platform and connected to the source of the fluid medium.