In this paper, an electro-active acoustic liner is used to lower the noise emissions of a turbofan engine. The liner is composed of an array of electro-acoustic absorbers covered by a wiremesh in order to protect the electrodynamic devices from the flow. The electro-active liner is operated using a pressure-based and current-driven control architecture, for the synthesis of specific acoustic impedances. The control strategy is either local or non-local.

Experiments are performed in the PHARE-2 test-rig at École Centrale de Lyon, representative of a real turbofan engine at the laboratory scale. Upstream and internal microphone arrays are used for the upstream noise emission measurements, and for the modal decomposition in the engine duct, respectively. Using a local control strategy, the obtained results underline the efficiency of the proposed concept on both tonal and broadband noise for a large range of operating points of the turbofan engine. Using a non-local strategy, non-reciprocity with respect to the azimuthal direction has also been shown for tonal noise with a predominance of contra-rotating modes.