NASA's Dryden Flight Research Center recently completed NASA's latest quiet sonic boom research study at Edwards Air Force Base.

The Waveforms and Sonic boom Perception and Response, or WSPR, project gathered data from a select group of more than 100 volunteer Edwards Air Force Base residents on their individual attitudes toward sonic booms produced by aircraft in supersonic flight over Edwards.

NASA and industry are studying technology that will reduce the noise and annoyance associated with sonic booms to the point where aircraft flying over populated areas at supersonic speeds do not disturb the peace, and aviation and governmental authorities may consider lifting prohibitions. But before the current restrictions on supersonic flight over land can be changed, much research is needed to understand how individuals and communities react to low-noise sonic booms.

WSPR's primary purpose is to develop data collection methods and test protocols for future public perception studies in communities that do not usually experience sonic booms. The base's unique flight-test airspace puts Edwards residents in a position to experience loud booms regularly, so their reactions to low-noise booms will be a valuable guide for future work in sonic boom perception and response.

"Understanding the study participants' responses to sonic booms is very important to NASA," said Larry Cliatt, Dryden's principal investigator for the research effort. "We're pleased with their participation."

Participants used a standard questionnaire to provide information every time they heard any sonic boom while at home. In keeping with the "there's an app for that" age, some participants responded using smart phones with apps supplied by the WSPR project. Other study participants used a web-based application, and some used paper forms.

For the supersonic flight portion of the research that occurred between Nov. 4 and Nov. 18, NASA F/A-18 aircraft flew specific flight profiles to generate booms, while NASA researchers monitored the flights, noting precise times and actual boom intensities recorded by ground instruments installed in the Edwards' base housing areas. Dryden conducted 22 flights during the test period, yielding 82 quiet sonic booms and five of normal intensity. The softest WSPR project boom was recorded at .08 pounds per square foot (psf) overpressure, while the loudest registered well within the normal range at 1.4 psf.

NASA Dryden takes great care to ensure that loud sonic booms do not impact residential communities, using preflight weather balloons and sonic boom analysis before every sonic boom research flight.

Dryden's partners in the WSPR effort include NASA's Langley Research Center, Wyle Laboratories, Gulfstream Aerospace Corp., Fidell Associates Inc., Pennsylvania State University and Tetra Tech. The cooperation of Edwards Air Force Base personnel was crucial to the study's success.

WSPR is funded by NASA's Aeronautics Research Mission Directorate and managed by the Supersonics Project in the directorate's Fundamental Aeronautics Program.