Aeroacoustics of Low Mach Number Flows

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Phased arrays

Abstract

In aeroacoustic measurements we are often faced with the problem of trying to determine the relative levels of two different sources or extracting the sound level of a source in a noisy environment. A classic example is measuring trailing edge noise from an airfoil in a wind tunnel. In this case we need to separate the sources at the trailing edge from the sources at the leading edge and also reject the background noise and reflection from the tunnel walls. To achieve this phased array technology has been developed over many years and has become a required tool for most aeroacoustic measurements in wind tunnels and on engine test stands. This chapter provides the basic concepts of array technology and the results ...