Using “multi-stage” compression, side channel pressure/vacuum generators produce low-pulsation suction and blast air. Perfected impeller design with curved blades guarantees optimum efficiency. Separation of the compression chambers on both sides of the impeller provides the capability of operating with a combination of suction and pressure with only one impeller. Intake filter, vacuum as well as pressure safety valve can be integrated as an optional extra in the patented design of the sound absorbers. The sound absorbers can be varied in length, affording flexible adjustment to available installation space.