Abstract: A vacuum brake booster having sound absorbing members affixed to the front and rear shells to attenuate sounds caused by air movement in the brake booster. The front shell is joined to the rear shell to define the housing for the brake booster. The housing is divided into a first chamber and a second chamber by a wall structure. The first and second chambers in a first mode of operation are designed to be in communication with a first source of fluid (vacuum) having a first fluid pressure while in a second mode of operation the second chamber is in communication with a second source of fluid (atmospheric air) at a second fluid pressure. In the second mode of operation, a pressure differential is created across the wall structure to produce an output force corresponding to an input force associated with a desired braking application.