Phased microphone arrays have become a well-established tool for performing aeroacoustic measurements in wind tunnels (both open-jet and closed-section), flying aircraft, and engine test beds. This paper provides a review of the most wellknown and state-of-the-art acoustic imaging methods and recommendations on when to use them. Several exemplary results showing the performance of most methods in aeroacoustic applications are included. This manuscript provides a general introduction to aeroacoustic measurements for non-experienced microphone-array users as well as a broad overview for general aeroacoustic experts.

Wind tunnels offer an effective tool to rapidly obtain data associated with flow over scaled or full‐scale models. Given their ubiquitous nature and utility, a wind‐tunnel design project is a fairly common yet complex exercise. We therefore review in this article the fundamentals of low‐speed wind‐tunnel design. The research goals and the specific measurement requirements are discussed, as well as the various space, budget, and power constraints that guide the tunnel design. Design guidelines are provided for the most common wind‐tunnel components, including flow conditioners, contraction, test section, diffuser, drive, and other optional components. Finally, facility characterization procedures are briefly summarized, including flow uniformity, turbulence intensity, and background noise and vibration levels.

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Microphone array processing algorithms often assume straight-line source-to-observer wave propagation. However, when the microphone array is placed outside an open-jet test section, the presence of the shear layer refracts the acoustic waves and causes the wave propagation times to vary from a free-space model. With a known source location in space, the propagation time delay can be determined using Amiet's theoretical method. In this study, the effects of shear layer refraction are examined using a pulsed laser system to generate a plasma point source in space and time for several different test section flow speeds and configurations. An array of microphones is used to measure the pulse signal, allowing for the use of qualitative beamforming and quantitative timing analysis. Results indicate that Amiet's method properly accounts for planar shear layer refraction time delays within experimental uncertainty. This is true both when the source is in the inviscid core of the open-jet test section, as well as when the source is located in different model wakes of varying complexity. However, the method breaks down where the thin layer assumption fails, such as in the region where the tunnel test section's open jet interacts with the facility jet collector.