From left, Haley Goldston, a research assistant with the University of Tennessee Space Institute (UTSI); Dr. Phil Kreth, an assistant professor with UTSI; and Justin Thomas, a test engineer with the 717th Test Squadron, 804th Test Group, Arnold Engineering Development Complex, look at shadowgraph data during an experiment in SL-2, a sea level turbine engine test cell at Arnold Air Force Base, Tenn., to study flow visualization for preemptive acoustic abatement in turbine test cells. (U.S. Air Force photo by Jill Pickett) (This image has been altered by obscuring a badge for security purposes.)