A membrane pump (1) for pumping a medium has a pump housing (2), a membrane (3) mounted to the pump housing and delimiting a pump chamber (4) inside the pump housing (2) and an actuating device for moving the membrane (3) to and fro to expand and contract the pump chamber (4). In a first operating mode, the actuating device moves the membrane (3) in a frequency suitable for pumping the medium into and out of the pump chamber (4), and in a second operating mode, the actuating device moves the membrane (3) in a frequency in the audible frequency region.