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Feature Story

Boeing engineers laid nearly 8 miles of cable and 65 high-fidelity microphones in the desert


Boeing engineers laid nearly 8 miles of cable and 65 high-fidelity microphones in the desert to capture low-frequency sonic boom waves as part of testing with NASA and other industry partners.

"Giant ear" captures sonic booms

Deep in the California desert, Boeing employees test and validate an acoustic array that ensures a better understanding of supersonic sound.

An F/A-18 (middle) flies directly over Boeing's innovative spiral array


An F/A-18 (lower right) flies directly over Boeing's innovative spiral array and an instrumented glider (upper left) during recent sonic boom testing near NASA's Dryden Research Center at Edwards Air Force Base in California.

In a dried up lakebed near NASA’s Dryden Research Center at Edwards Air Force Base in California, Boeing engineers meticulously peppered the ground with dozens of microphones spanning the length of more than six football fields and the area of a 9-hole golf course.

Once in place, NASA pilots flew nearly 100 passes over a unique, 9-armed spiral-shaped array. The microphones captured low-frequency, thunder-like waves created by F/A-18Bs flown just over the speed of sound.

The sound and fury was all part of a recent two week NASA test involving Boeing research, flight test, business units, a university and several other companies to test and validate acoustic array systems that help develop a better understanding of the impact of supersonic sound waves over land.

“We basically created a giant ear in the middle of the desert,” said Rebecca Shupe, a Boeing acoustics engineer.

While Boeing has no current plans to build a commercial supersonic jet and the Federal Aviation Administration does not allow civil supersonic flight over land, NASA and the FAA have established a test program and an academic center to further investigate sonic booms. Together, they are working with Boeing and other industry leaders in the testing.

“We basically created a giant ear in the middle of the desert.”

“These tests will shed light on the boundaries of the sonic boom carpet, in particular when a boom diminishes -- which can happen within a relatively short distance,” said Boeing project manager Matt Moore. “With that information, we can use the data from our state-of-the-art measurement system to create an accurate prediction tool for sonic boom sound waves.

“The main concern with sonic boom waves is that they tend to startle people.”

Unlike previous tests that arranged microphones in a straight line, this time Boeing engineers installed 65 high-fidelity microphones in a spiral pattern, and utilized its latest technologies to capture the booms as they moved across the expansive desert. For this round of testing, Boeing hauled in thousands of pounds of equipment, including nearly 8 miles (12.8 kilometers) of cable.

“It’s vital that we participate in these types of tests so we can calibrate our own technology, ensuring that Boeing can maintain the leading edge when it comes to our customer’s needs,” Shupe said.

Dassault Aviation, Cessna, Gulfstream, Penn State University, Wyle Labs and the Japanese Aerospace Exploration Agency also took part in the process, with several companies testing their own arrays.

“From the commercial perspective, Boeing is always looking at advanced technologies and determining their readiness for future applications,” said Kourosh Hadi, director of Airplane Product Development. “However, just because advanced technologies are being studied does not necessarily mean that Commercial Airplanes will incorporate that innovation on a future airplane model.”

Boeing has worked with NASA to understand sonic booms for decades, including a sonic boom test program that began in 2005, with eight tests conducted since. Future testing with NASA is being discussed.