The Lockheed Martin Low Speed Wind Tunnel (LSWT) is a closed-return wind tunnel with two solid-wall test sections. This facility originally entered into service in 1967 for aerodynamic research of aircraft in low-speed and vertical/short take-off and landing (V/STOL) flight. Since this time, the client base has evolved to include a significant level of automotive aerodynamic testing, and the needs of the automotive clientele have progressed to include acoustic testing capability. The LSWT was therefore acoustically upgraded in 2016 to reduce background noise levels and to minimize acoustic reflections within the low speed test section (LSTS). The acoustic upgrade involved detailed analysis, design, specification and installation of acoustically treated wall surfaces and turning vanes in the circuit as well as low self-noise acoustic wall and ceiling treatment in the solid-wall LSTS. The preservation of the aerodynamic flow quality and the reduction in background noise levels in the LSTS were demonstrated by a series of measurements that were performed both prior to and after the acoustic upgrade.