Abstract: A muffler comprising a main body having a downstream end and an upstream end relative to gas flow. There is an inner vessel within the main body to divide the main body into an inner chamber and first and second outer chambers. A resonating chamber within the inner chamber divides the inner chamber into first and second inner chambers. The resonating chamber has a perforate wall on its upstream side. An inlet pipe extends into the upstream end of the main body and terminates in a downstream end communicating with the first outer chamber and the first inner chamber. An outlet pipe extends into the upstream end of the main body and terminates in the second outer chamber and in the second inner chamber. In addition there is an inner pipe communicating the first outer chamber, the first inner chamber and the resonating chamber. The further inner pipe communicates the second outer chamber, the second inner chamber and the resonating chamber.