Abstract: This relates to a novel design for lobed pistons for rotary positive displacement pumps. By segmenting the pistons and allowing the pistons segments to cooperate as independent pumps, the present noise and vibration produced by these pumps can be reduced in intensity and smeared in time. The pistons are segmented by rotating one segment with respect to another so that the lobes have angular rotational displacement. The best angular displacements are 45 degrees for two lobed pistons and 30 degrees for threes lobed pistons. As the pistons contrarotate in the pump the angular displacement must be opposite in sense, to allow segment cooperation. Allowing the segmented compression chambers to interact at the outlet, and providing a throttle valve between segments further reduces noise and vibration, giving a far smoother discharge flow and reduced pressure fluctuation. In another embodiment throttle valves are placed at the end of a conventional pistion to reduce noise and even discharge flow.