Modeling of acoustic lined duct with and without grazing air flow by an analytical method

An analytical method is proposed to characterize the sound acoustic transmission in a rectangular lined duct with and without grazing air flow. The acoustic wave number in the duct is determined using Taylor series expansion. The proposed method is validated by comparison with a finite element method in grazing air flow environment and experimental measurements at grazing sound incidence for the case with no flow. Excellent agreement is found in both configurations. The proposed method is used for sensitivity analysis of acoustic duct lined with micro perforated panel absorber in order to evaluate the impacts of the inputs parameters on the transmission loss of the duct. It is shown for a constant sound pressure level that the transmission loss of the duct is very sensitive to the cavity depth of the absorber while the resonance of the transmission at high sound pressure level is controlled by the perforation ratio of the panel. The effects of the perforation diameter and the plate thickness are negligible for higher pressure excitation and the impact of the sound pressure level on the transmission is preponderant.