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NASA Captures Unprecedented Images of Supersonic Shockwaves (phys.org)
As NASA looks into developing planes that can fly faster than sound without creating "sonic booms," the space agency has captured unprecedented photos of the interaction of shockwaves from two supersonic aircraft. Phys.Org reports: When an aircraft crosses that threshold -- around 1,225 kilometers (760 miles) per hour at sea level -- it produces waves from the pressure it puts on the air around it, which merge to cause the ear-splitting sound. In an intricate maneuver by "rock star" pilots at NASA's Armstrong Flight Research Center in California, two supersonic T-38 jets flew just 30 feet (nine meters) apart below another plane waiting to photograph them with an advanced, high-speed camera, the agency said. The rendezvous -- at an altitude of around 30,000 feet -- yielded mesmerizing images of the shockwaves emanating from both planes. You can view all of the photos via NASA.
I've heard plenty of sonic booms and I'd be hard pressed to describe them as 'ear-splitting'.
You must have been far, far away from the sonic booms. I lived about 15 miles from a former military air base. Jet jocks were often goofing around and busting the sound barrier. The noise is LOUD and startling!
2nd link says this: "The images were captured during the fourth phase of Air-to-Air Background Oriented Schlieren flights, or AirBOS"