Active Control of the Directivity of Fan Tones Noise

Abstract : Experiments on a fan model (diameter 47 cm 47 blades, nominal rotation speed 12,6OO rpm) installed in an anechoic test cell have recently been carried out to assess the technique of Active Noise Control (ANC) applied to reduce the tones noise at the blade passage frequency This paper describes in details the test model with the selected test configurations the test facility and the ANC system. Having already demonstrate the feasibility and the interest to reduce engine tones by application of this technique the objective of this study was to evaluate the acoustic benefits brought by this technology to check the robustness of the controller especially with engine rpm variations and to identify the realistic and promising configuration in view of engine applications Loudspeakers wall -mounted and located in a duct cross-section close to the fan source were used as secondary sources Error sensors were successively located outside the inlet and wall-mounted in the duct according to different distributions.