Beamforming Algorithm for Distributed Source Localization and Its Application to Jet Noise

A new algorithm for estimating noncompact, distributed sources by means of phased array microphone measurements is presented and experimentally implemented to determine the noise source distribution in a subscale jet flow. Conventional beamforming techniques, developed for spatially well-separated point sources, can lead to significant errors when applied to reconstruct continuous source distributions such as jet noise. A new beamforming approach is developed for estimating such continuous source distributions. The objective is to recover the average source strength over a small region around each focus position as opposed to seeking the exact source strength at each spatial location as in conventional approaches. This strategy overcomes the drawbacks of conventional methods and yields a beamformer with uniform spatial resolution and accuracy over a large frequency range. The measurement technique is applied to the localization of broadband noise sources in a high-subsonic, heated, turbulent jet flow and shows good comparisons with prior measurements using other techniques.