De-Dopplerization of Acoustic Measurements
Technical Report,26 Jun 2016,17 Jul 2017
711 Human Performance Wing Wright-Patterson AFB United States
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To ensure acoustic directivity patterns are valid across a wide range of sound source speeds the effect of Doppler shifting must be removed from acoustic measurements used to build directivity patterns. Traditionally, obtaining spectral information by analyzing acoustic measurements with Fourier transforms requires complex resampling to overcome stationary signal requirements. Here, a simple shifting of band energy obtained from fractional octave band digital filters generates a de-Dopplerized spectrum without complex resampling algorithms. An equation defining the amount of energy shifting required is derived from fractional octave center frequencies. This equation is applied to a numerical simulation and an overflight measurement to remove the Doppler affect in spectral data. The de-Dopplerization through application of energy shifting accurately removes vehicle motion effects from acoustic measurements without complex resampling.