"No other wind tunnel runs quietly while conducting experiments in airstreams traveling at Mach 6 – six times the speed of sound, said Steven Schneider, an aerospace engineer and professor in Purdue's School of Aeronautics and Astronautics.
Researchers will use the $1 million wind tunnel to help design advanced aircraft that travel at hypersonic speeds, or faster than Mach 5, which is about 4,000 miles per hour at sea level." [link]:
