Acoustic liner for gas turbine engine

The liner system (50) includes a mode-scattering segment (48) providing a reactance between -12 and -2 rho c and a sound absorbing segment (40) providing a reactance between -1 and -0 rho c, to provide a reactance discontinuity, such that mode-scattering of the sound field enables the sound absorbing segment to further absorb the scattered sound. An independent claim is also included for ducted fan gas turbine engine.