9- by 15-Foot Low-Speed Wind Tunnel Acoustic Upgrade Part 2: Improvement Comparison

This report describes an acoustic improvement project carried out in the NASA Glenn Research Center (GRC) 9- by 15-Foot Low Speed Wind Tunnel (9x15 LSWT) and the effect on the acoustic measurement capabilities of the facility. The improvement project began in June 2017 and ended in March 2019, with some work stoppages in between. The main purpose of the project was to reduce the background noise of the facility to enable better signal-to-noise ratio measurements of quiet aircraft propulsion concepts. The term background noise refers to the noise measured inside the facility without a model installed. This report discusses the details of the project, the
motivation for the upgrade and the history of the facility background noise levels that motivated the upgrade. This report is one of a two-volume set documenting the 9x15 LSWT acoustic improvement. The companion report[1] documents the “supporting studies” that were conducted as part of the improvement project, but do not relate explicitly to the 9x15 LSWT. The present report is focused specifically on studies conducted by NASA regarding the 9x15 LSWT and thus may be less broadly
applicable to other facilities or projects.