Getting Loud Now Enjoy Peace and Quiet Then

In an ironic twist, NASA is using supersonic aircraft to produce amped-up, super-loud sonic booms in an effort to understand how to minimize their startling impact and thereby be able to design future quiet supersonic aircraft.

"The ultimate goal is to allow supersonic transportation over land," said Edward Haering, principal investigator for the Superboom Caustic Analysis and Measurement Program, or SCAMP, at NASA's Dryden Flight Research Center in California.

Researchers recently employed a two-mile long string of microphones to record the thunder of an accelerating F/A-18 jet for the SCAMP project.

"When a supersonic aircraft accelerates to its cruise speed, a focusing effect occurs that makes the sonic boom five to 10 times louder than its normal cruise sonic boom over a small region,” said Haering. "This effect is similar to how light rays are focused by a lens."

SCAMP measured these focused booms to help ensure that tomorrow's supersonic jets are quiet in all phases of flight, including acceleration.

The measurements will be used to validate computer prediction tools that will be used in the design of future quiet supersonic aircraft. If the predictive tools can accurately mirror the louder-than-normal booms that were generated through SCAMP, then researchers will have confidence that they are capturing the right acoustics and aerodynamics effects, and they can then be used with confidence to guide the design of supersonic aircraft whose sonic booms are quieter than have ever been achieved before.

The primary ground microphone array was nearly two miles long and consisted of a straight row of 81 microphones set 125 feet apart along an east-west dirt road. An Edwards Air Force Base staff biologist experienced with desert environments helped keep the project’s sensor locations away from sensitive species.

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