Analysis of Coherent Power Techniques for Aeroacoustic Testing

Coherent power techniques are often used in aeroacoustic source analysis.  These techniques involve certain sets of assumptions regarding the nature of an acoustic source field, which may not hold in aeroacoustic measurements.  This paper presents fundamental derivations and analysis of coherent power signal processing techniques to assess their validity in aeroacoustic experiments.  Assumptions regarding source field incoherence are applied for groups of sources to examine method limitations.  Monopoles are considered, along with dipoles so that directivity effects are included.  Measurement schemes characteristic of those performed in the University of Florida Aeroacoustic Flow Facility are used to provide example dimensional results of coherent power analysis.  In this manner, the accumulated errors in coherent power analysis due to the presence of a large number of incoherent sources are examined.