Application of noise source identification using extended clean-sc and a new denoising method to a turbofan engine measurements outdoors

Last few years, acoustic measurements of a turbofan engine, DGEN380, have been conducted in the open test site by JAXA and Brüel & Kjær. The authors showed an ability of the extended CLEAN-SC which suggests a potential of evaluating directional contributions of jet noise sources in the paper presented at BeBeC 2018. The previous paper described the extended CLEAN-SC using reference signals selected from the array microphones to obtain contribution of sources correlating to the reference signal. In this paper, to evaluate more about directional contributions practically, independent reference microphones were placed on the side-line on the ground parallel to the jet axis instead of using signals selected from the array microphones as reference signals. In the case of measurements conducting outdoors or in a wind tunnel, flow-induced noise in microphones often becomes a problem. Therefore, this paper also describes a new denoising method, Canonical Coherence Denoising (CCD), which was proposed by Hald, and tries it in the extended CLEAN-SC calculation in order to reduce flow-induced noise.