Stand-Alone Extraction of Cyclostationary Broadband Components from Aeroacoustic Signals

Abstract

Aeroacoustic signals, as typically returned by recordings of pressure fluctuations generated by rotating machines, often exhibit a strong contribution of broadband components. Separate analysis of the various sources of broadband noise is important from an engineering point of view, as they relate to different physical mechanisms. It is yet technically difficult to achieve, as the corresponding signals overlap in both time and frequency. A solution is proposed based on the angle–time cyclostationary property of broadband noise produced by rotating sources. Cyclostationary broadband components can thus be extracted, resynthesized in the time domain, and analyzed individually as if they were measured alone with all other interfering sources switched off. A special effort is made to render the methodology as stand-alone as possible by providing criteria for automatically setting up the leading parameters. The methodology is illustrated in counter-rotating open rotor data, where cyclostationary broadband contributions from the rear and front rotors and their interaction are individually extracted.