Using numerical and experimental two-port determination techniques for the aeroacoustic characterization of confined subsonic flow applications

For the aeroacoustic design of flow duct systems such as automotive intake and exhaust system and HVAC ducts both the convective noise propagation effects and the aerodynamic noise generation mechanisms should be taken into account. Often, a compromise has to be made between maximizing the total noise attenuation and minimizing the aerodynamic flow-noise generation. A two-port characterization, describing an arbitrary type of duct element using an acoustic transfer matrix, allows a straightforward evaluation of both aeroacoustics properties for the various subcomponents of the flow duct network. In this paper, the use of both a numerical and an experimental two-port determination technique for the aeroacoustic characterization of duct systems is presented and evaluated. The two-port characterization methodologies are applied to various, simplified, automotive muffler configurations with varying geometrical complexity; including perforated ducts, sound-absorbing materials, extended inlet and outlet pipes and baffles. In this way, the advantages and limitations of state-of-the-art numerical and experimental aeroacoustic characterization techniques are highlighted and their possible use for the aeroacoustic design of flow duct networks is illustrated.status: publishe