It is the goal of this paper to advance the field of noise measurement techniques to better understand the fundamental guiding principles of noise generation. This is accomplished in this study by demonstrating the capabilities of ultrahigh speed Rainbow Schlieren Deflectometry (UHS-RSD) technique to visualize and quantify, in real-time, sound waves propagating from a supersonic cold air jet. Basic optical theory states that light rays passing through varying density transparent medium undergo deviation from their original path because of refraction. Therefore, an experimental setup was developed to direct parallel white light rays through a supersonic air jet. The variation in density field created in the jet stream causes light rays to deviate from their original path. The UHS-RSD technique employs aforementioned technique and enables mapping of the light deflection angle, a measure of deviation of a light ray from its original path due to refraction. Deflection mapping process is realized through variation in color (hue) between an image without and with test medium. Since all information in the field of view can be captured in one instant in time this technique provides us with a means to determine full field of view characteristic scalar properties of any transparent flow. The current experiment captures sound waves emanating from a supersonic cold air jet at high spatial and temporal resolution while still maintaining the high hue sensitivity needed to detect the small pressure fluctuations characteristic of sound waves. It is expected that sound probe data showing general maximum sound generation will support the visual UHS-RSD data where visible pressure gradient waves are seen propagating from the jet flow.
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