Patent ID: 8727707

Claim:
A turbofan gas turbine engine comprising: a fan, an intake duct with a liner upstream of the fan, a fan rotor having a plurality of fan blades, the intake duct liner including an acoustic liner positioned upstream of the fan and a buzz-saw tone noise liner positioned upstream of the acoustic liner, the buzz-saw tone noise liner has a greater depth than the acoustic liner, wherein the buzz-saw tone noise liner is positioned substantially at, or near, an upstream end of the intake duct, the intake duct has a lip and the buzz-saw tone noise liner is positioned at, or near, the lip, which is at a position selected from the group consisting of a position of minimum cross-sectional area of the intake duct and a position close to a position of minimum cross-sectional area of the intake duct, and the buzz saw tone noise liner is positioned upstream of the position of minimum cross-sectional area of the intake duct.