Sonic booms created by aircraft flying faster than the speed of sound certainly aren’t known for being faint, but rather for their loud, make-you-jump startle effect for those who experience them. However, sonic booms have a quieter, fainter side, too.
NASA’s Supersonics Project is embarking on its latest effort to characterize or define that fainter side of sonic booms as a NASA F/A-18 aircraft takes to the air in a project called Farfield Investigation of No Boom Threshold, or FaINT.
As the latest in a continuing progression of NASA supersonics research projects aimed at reducing sonic boom levels, FaINT is designed to enable engineers to better understand evanescent waves, an acoustic phenomenon that occurs at the very edges or just outside of the normal sonic boom envelope.
For an aircraft flying at a supersonic speed of about Mach 1.2 or less at an altitude above 35,000 feet, the shockwaves being produced typically do not reach the ground, so no sonic boom is heard. This is because shockwaves from an aircraft flying supersonically at higher altitudes are refracted, or bent upwards, as they enter warmer air closer to the ground, due to the fact that the speed of sound increases with air temperature.
NASA’s Supersonics Project is embarking on its latest effort to characterize or define that fainter side of sonic booms as a NASA F/A-18 aircraft takes to the air in a project called Farfield Investigation of No Boom Threshold, or FaINT.
As the latest in a continuing progression of NASA supersonics research projects aimed at reducing sonic boom levels, FaINT is designed to enable engineers to better understand evanescent waves, an acoustic phenomenon that occurs at the very edges or just outside of the normal sonic boom envelope.
For an aircraft flying at a supersonic speed of about Mach 1.2 or less at an altitude above 35,000 feet, the shockwaves being produced typically do not reach the ground, so no sonic boom is heard. This is because shockwaves from an aircraft flying supersonically at higher altitudes are refracted, or bent upwards, as they enter warmer air closer to the ground, due to the fact that the speed of sound increases with air temperature.
For more info, visit: http://www.nasa.gov/topics/aeronautics/features/faint_sonic_booms.html
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