Membrane pump operating in both audible and inaudible frequency regions

Method of producing a sound in a pumping system, the pumping system comprising a membrane pump (1) for pumping a medium into or out of a vessel, the membrane pump (1) comprising:

• a pump housing (2),
• a membrane (3), which is mounted to the pump housing (2) and delimits a pump chamber (4) inside the pump housing (2),
• an inlet (5) for feeding medium into the pump chamber (4), the inlet (5) having a first non-return valve (6) connected thereto,
• an outlet (7) for discharging medium from the pump chamber (4), the outlet (7) having a second non-return valve (8) connected thereto,
• an actuating electromagnet (9) for moving the axle (11) and membrane (3) to and fro to expand and contract the pump chamber,
• wherein the actuating electromagnet (9) operates in two separate and distinct operating modes,
• in a first operating mode moving the membrane (3) in an inaudible frequency suitable for pumping a medium into and out of the pump chamber (4), and
• in a second operating mode moving the membrane (3) in a frequency in an audible frequency region for generating an audible alarm, and
• a control unit for increasing the frequency by activation and deactivation of the electromagnet (9) to increase vibration frequency of the membrane (3) to vibrate in the second operating mode where response time of the oscillating membrane (3) results in a smaller oscillation amplitude of the membrane (3) and the non-return valves (6, 8) are unaffected by the membrane (3) oscillation and thus prevented from opening and closing, and
• the membrane (3) produces a sound by being moved in the frequency in the audible frequency region by the actuating electromagnet (9).