A transfer duct and an associated active tip clearance control system of a gas turbine engine are disclosed. In one embodiment, the duct comprises: an upstream duct portion for fluid communication with an air source; a downstream duct portion for fluid communication with a manifold for directing the air toward a rotor case; and a noise-mitigating device disposed between the upstream duct portion and the downstream duct portion. The duct may define an abrupt change in internal cross sectional area between the upstream duct portion and the noise-mitigating device.
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