Summarizing the near-field acoustical environment during liftoff of Artemis I

Far-field acoustical measurements are often used to study source-level characteristics of rockets. However, to adequately mitigate vibroacoustic loading of launchpad environments, near-field data are needed to understand the rocket’s noise source origins. This paper describes an analysis of acoustic data collected on the Mobile Launcher (ML) tower during NASA’s Artemis I launch. While previous work has studied Space Launch System (SLS) far-field acoustics, this work uses sensors placed ∼2–4 effective nozzle diameters from the SLS centerline. Maximum overall sound pressure levels along the ML tower-back reach ∼162 dB and exceed 170 dB at the ML tower-front, originating ∼10 effective exit diameters downstream of SLS’s nozzle exit plane. Data on the tower-front and -back were combined to calculate the running octave-band sound pressure levels from 8–1,000 Hz. This frequency-dependent model for plume source characteristics suggests that the peak noise radiation spans from 16–125 Hz, a significantly wider frequency range than in the far field and evidence that SLS’s noise originates from both individual- and merged-plume zones.