04.09.19

NASA tests 30-mile-long microphone array in supersonic jet trial

Microphone
The Mojave microphone array

NASA claims it has successfully tested a 30 mile long microphone array in the Mojave Desert as part of the preparations for the test of the space agency’s quiet supersonic ‘X-Plane’, the X-59.

Multiple microphone stations will be used in the ‘CarpetDIEM’ flight series, a series of sound measurements using the microphone array on the ground that will cover the entire width area where the X-59’s ‘quiet’ sonic thumps can be heard.

The microphones will be monitoring the X-59 during an acoustic validation phase in which the arrays of ‘specially-configured’ microphones will be deployed to measure the sonic ‘thumps’ of the X-59 to verify that the secretive aircraft is as quiet as NASA predicted. 

The goal of CarpetDIEM is to practice deploying a large-scale microphone array, gaining valuable lessons on the array’s ideal configuration, instrumentation, and logistics.

X59

Ed Haering, NASA’s principal investigator for CarpetDIEM said: “The X-59 is designed to have quiet sonic booms that won’t be disturbing to the people, but first we actually have to go out and prove it.

“NASA will do that by flying the aircraft and taking real measurements on the ground before we eventually fly it over communities, to make sure that it is as quiet as it should be.”

The array uses high-fidelity microphones that can measure 50,000 samples per second, allowing researchers to obtain accurate sound data and assess the loudness of the sonic booms. 

To test the array, NASA flew an F/A-18 fighter jet to produce sonic booms under the designated supersonic corridor, running from Nevada toward NASA’s Armstrong Flight Research Center in California. 

Juliet Page, a physical scientist with Volpe said: “We have a series of microphones set up, and the various sites have different configurations.

“We have microphones oriented in different configurations, including inverted, vertical, horizontal, some with different wind screens, and we’re evaluating the acoustic performance and the difference between the different configurations in preparation of the X-59.”

The data from the test flights will be turned over to the Federal Aviation Administration, with the aim of potentially establishing new sound-based rules for supersonic flight over land, opening the door to future faster-than-sound commercial cargo and passenger air travel.