Vacuum pump with a chamber (1) having, on one side, an intake (2) for pumping gas and, on the opposite side, an outlet (3) for the gas, displacement elements (4) being provided to drive the gas from the intake (2) towards the outlet (3), the displacement elements (4) including at least a vibrating element (4) for generating sound waves moving in the chamber (1), elements for closing (6) the outlet (3) being provided synchronously co-operating with the displacement elements (4) so as to clear the outlet opening (3) when the gas pressure in the proximity of the outlet (3) is higher than that in the proximity of the intake (2).