A fluid coupling conduit (6, 50, 70, 104, 134) includes an inlet end (28, 52, 76, 110, 140) structured to receive a flow of breathing gas, an outlet end (32, 56, 78, 112, 142) fluidly coupled to the inlet end and defining an outlet opening, a central chamber portion (36, 60, 80, 124, 145) positioned between the inlet end and the outlet end, the central chamber portion having an outer wall (38, 62, 82, 116, 146) positioned opposite the outlet opening. The outer wall has a plurality of exhaust gas orifices (40, 64, 84, 118, 148) extending therethrough. A number of sound attenuating structures are disposed in the central chamber portion between the outlet opening and the outer wall. The sound attenuating structures including a plurality of surfaces structured to reflect sound waves associated with exhaust gas flow through the fluid coupling conduit.