One way of attenuating noise propagating in ducts or pipe systems is to use one or more perforated pipes, each of which is specifically designed for optimal performance at a particular frequency range. In this study, transmission loss performance and pressure loss characteristic of a perforated pipe in an expansion chamber with the mean flow are investigated experimentally. The effects of both geometrical design parameters and flow velocity on both acoustical and pressure performances are investigated on the muffler. In order to determine the transmission loss characteristics, the mean flow velocity is considered and two load method combined with wave decomposition method is applied. Results of some experimental measurements are discussed in this paper. Pressure loss measurements are performed at several mean flow velocities for different geometric combinations.