A thunderous rumble heard and felt through Cooke County on Thursday afternoon — briefly rumored to be an explosion — has been speculated to be a sonic boom, a sound that officials admit has become rare.
Emergency Manager Ray Fletcher said the rumble, heard around 4:30 p.m., was possibly a sonic boom but didn’t appear to have been caused by anything else.
“Nobody’s confirmed that to me but I suspect that’s probably what it was,” he said Friday, adding that no explosions were reported. “As far as I know, there were no calls received that anything else had happened. No reports of damage and no calls other than one or two, questioning, ‘What was that?’”
What a sonic boom is
United States Air Force (USAF) information defines a sonic boom as an “impulsive noise similar to thunder, caused by an object moving faster than sound, about 750 miles per hour at sea level.” An aircraft traveling through the atmosphere continuously produces air-pressure waves similar to the water waves caused by a ship's bow. When the aircraft exceeds the speed of sound, these pressure waves combine and form shock waves which travel forward from the generation or “release” point. The USAF information added that as an aircraft flies at supersonic speeds it is continually generating shock waves, dropping sonic boom along its flight path, similar to someone dropping objects from a moving vehicle. From the perspective of the aircraft, the boom appears to be swept backwards as it travels awayfrom the aircraft. If the plane makes a sharp turn or pulls up, the boom will hit the ground in front of the aircraft.
According to the USAF information, the sound heard on the ground as a “sonic boom” is the sudden onset and release of pressure after the buildup by the shock wave or “peak overpressure.” The change in pressure caused by sonic boom is only a few pounds per square foot, about the same pressure change experienced on an elevator as it descends two or three floors, in a much shorter time period. It is the magnitude of this peak overpressure that describes a sonic boom.
Fletcher added that he didn’t know if the flight was military, but said a sonic boom would come most likely from a military aircraft gone supersonic.
They aren’t heard much in this region, he offered, due to a downturn in flight operations.
“It’s completely subjective — but I think it’s rare because of how many fewer military aircraft we have flying around today than two or three decades ago,” he said. “It’s a considerably smaller number, and that may be one reason.”