High area ratio rockets generate strong vibro-acoustic loads primarily during transient operations, like start-up and shut-down of the engine. These loads can adversely affect the launch vehicle and its payload. Thus, an accurate prediction of the loads produced during engine start-up is pertinent to the safety and reliability of the launch vehicle. The present work focuses on developing a robust framework for predicting these loads using laboratory scale rocket nozzles tested in the fully anechoic chamber at The University of Texas at Austin. This encompasses corrections for the observer position relative to the prominent source region, as well as scaling factors to correct for geometric factors. The test campaign encompasses single, two, three and four nozzle clusters, as well as differences in nozzle geometry and operating conditions (nozzle pressure ratio).