Abstract: The 9- by 15-Foot Low Speed Wind Tunnel (9×15 LSWT) at NASA Glenn Research Center was built in 1969 in the return leg of the 8- by 6-Foot Supersonic Wind Tunnel (8×6 SWT). The 8×6 SWT was completed in 1949 and acoustically treated to mitigate community noise issues in 1950. This treatment included the addition of a large muffler downstream of the 8×6 SWT test section and diffuser. The 9×15 LSWT was designed for performance testing of VSTOL aircraft models, but with the addition of the current…