A vehicle exhaust system includes a subsystem having an exterior pipe formed of a polymer. A rigid liner extends along the length of the exterior pipe and defines a passageway. A fiber insulating layer is formed between the rigid liner and the exterior pipe. The liner is formed to define at least one groove circumscribing the periphery of the passageway. The groove defines a region of increased volume of the exhaust passage along the length. The liner is further formed to define at least one void extending between the wall of the liner and the insulating layer, around the periphery of the passageway. A plurality of apertures in the liner, allow sound waves to pass from the passageway into the fiber insulating layer, and into the void.