Application of active control techniques to the turbomachine fan noise reduction

Fan noise is a dominant source in future high‐bypass engines with a lower and more extended frequency signature. The reduced efficiency of passive liners with thinner and shorter nacelles leading to a more severe noise legislation requires work on active technologies in order to reduce even better the fan noise radiation (especially tones) in the near and far fields. This paper deals with active noise control (ANC) applied to the reduction of fan tones. The described investigation is an experimental study performed on a fan model installed in an anechoic chamber. Error sensors are successively located in the near‐field radiation and flush mounted in the forward and aft duct fan. Loudspeakers are used as actuators to generate a secondary acoustic field. A moving antenna in the far field measures the noise radiation and the zones of silence. A new multi‐channel controller, highly efficient in terms of frequency and channel number, is used. Transfer functions between actuator and sensors are analyzed and num...