A pulse generator (18) for use with a system (10) for mobilizing lung secretions comprising: a generator body (44) ； a plunger (26) disposed inside the body (44), the plunger (26) having a first end and a second end and being moveable to regulate fluid flow between a plunger port (24) and an outlet port (40)； a diaphragm assembly (106) having an input side and an output side； a first diaphragm (28) between the second end of the plunger (26) and the diaphragm assembly (106), the first diaphragm (28) having a plunger side facing the plunger (26) and an opposite side facing the diaphragm assembly (106)； a fluid channel extending from the outlet port (40) to the input side of the diaphragm assembly (106)； an orifice (38) and a valve (36) residing in the fluid channel.
