On October 14, 1947 a new sound was heard for the first time. USAF Captain Charles E. "Chuck" Yeager in the Bell X-1 broke the sound barrier high over the Air Force Flight Facility located in the Californian Mojave Desert. The recorded world record speed was Mach 1.07.
The X-1, named "Glamorous Glennis" after Yeager’s wife was dropped from a B-29 flying at 250 mph and 20,000 feet above the desert floor. After the drop from the B-29 the ensuing climb made at .85-.88 Mach. At 42,000 the speed increased to .98 Mach then the needle of the machmeter fluctuated momentarily, then passed off the scale. The supersonic era had begun.