Abstract: The noise sources in an axisymmetric jet are located mainly near the nozzle, and its strength decreases continuely with increase of X/D. According to this theoretical result, a round baffle-absorption muffler was designed and studied in experiments. The muffler reduces mainly jet noise of which frequencies are higher than 1 kHz. It is advisable to design the front length in the muffler is 25 D. The muffler can be used not only for a exhausting jet, but also for a working jet.