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To suppress combustion instabilities, perforated liners can be fitted along the bounding walls of a combustor to provide acoustic damping. These liners are typically subjected to a low-Mach-number bias flow (a cooling flow through perforated holes), and they tend to be effective only over narrow frequency ranges. To investigate the damping effect of perforated liners on plane acoustic waves and to increase their effective frequency range, experiments and numerical simulations are carried out. An acoustically driven pipe system containing a lined section was designed and experimentally tested. The length of the pipe system, along with the bias flow rate, could be varied. The experimental results showed that the liner damping depended on both the pipe length and the bias flow rate, in agreement with predictions from the numerical model presented by (Eldredge, JD, and Dowling, AP,“The Absorption of Axial …