Abstract: A linear pump having an axially aligned cylinder and piston arrangement driven by an electromagnet motor has an exhaust chamber defining a cavity covered by a diaphragm. The diaphragm is movable toward the cavity in response to pressure fluctuations in the exhaust chamber to attenuate pulsations in an air stream exiting the exhaust chamber. A diaphragm is mounted over the recessed cavity by a support ring having an open center allowing air to act against the diaphragm.