I. Introduction he noise environment around airport is a major cause of concern within the world, with many local communities exposed to high levels of aircraft noise; the effective reduction of such a ‘noise pollution’represents both a technical and a financial important challenge for the incoming years. The noise generated by an aircraft in approach or take-off flights has two main contributions; firstly the engine noise, that results from both the jet and the turbomachinery (fan, turbine, combustion) sound emissions. And, secondly, the airframe (or aerodynamic) noise, which is induced by the interaction between turbulent flows and solid structures (wings, slats, flaps and landing gears). Although the engines' contribution to the overall aircraft noise is largely dominant at takeoff, it is equalled by the airframe one in the approach flight phase, during which the engines' thrust is considerably