Investigation of measured sonic boom variability and ambient noise coherence across a 400-ft linear array

Abstract

In preparation for the NASA X-59 flight test campaign, it is relevant to understand the variability of measured sonic boom metrics over short distances. One of the measurement stations at the 2019 NASA Carpet Determination in Entirety Measurements (CarpetDIEM) campaign consisted of a 400-ft linear array of seven microphones beneath and perpendicular to the flight track. The purpose of this array was to assess variability in CarpetDIEM boom characteristics over the array aperture. Analysis shows that all candidate metrics can vary by more than 6 dB across the array and that this variability appears to be normally distributed about a mean value for the array. Confidence intervals for several boom metrics are discussed. The ambient noise coherence across the array is also discussed in relation to the sonic boom metrics. [Work supported by NASA Langley Research Center through the National Institute of Aerospace.]