NASA to survey Galveston residents on sonic thump
By Keith Button|May 2018
In November, residents of Galveston, Texas, should hear a beta version of the double-thump sound that NASA expects will be generated by its planned “low-boom” supersonic X-plane when it starts flying in 2022.
NASA knows that if commercial jets are to fly supersonically in U.S. skies one day, residents must find the noise tolerable. The question is how to gather enough data to define what is tolerable. So, the agency plans to simulate the sounds of the X-plane by flying F/A-18s about 40 kilometers offshore from Galveston and into a supersonic dive from 50,000 feet. The agency will try out community surveying techniques that it will apply during the flights of the Lockheed Martin-built Low-Boom Flight Demonstrator that will test noise reduction designs for commercial developers.
In the past, NASA has surveyed residents of Edwards Air Force Base, California, about jet noise and asked volunteers to sit inside a simulated home, called the Interior Effects Room, at Langley Research Center in Virginia. With the Galveston flights, NASA hopes to learn how to survey a large community that’s largely unfamiliar with the noise from supersonic airplanes, says Peter Coen, project manager of NASA’s Commercial Supersonic Technology Project.
The techniques need to be ready by 2022, when NASA plans to fly the X-plane over multiple communities and then survey the residents, storing the results in a database. The FAA and the International Civil Aviation Organization could then set standards for acceptable noise levels for overland commercial supersonic aircraft, which are currently banned in the U.S. and other jurisdictions.
“Right now, we’re just trying to get a handle on how do you engage a community; how do you engage their elected leadership in a positive way; how do you plan a deployment for airplanes; how do you deploy acoustic sensors; how do you engage survey participants to conduct such a survey,” Coen says.
NASA will survey Galveston residents through a web application, asking them what they heard and what their response was to the sound. The double-thump noise to be emitted by the low-boom demonstration aircraft, and replicated by the NASA F/A-18 research planes, sounds like a next-door neighbor closing his car door, Coen says. Because survey subjects on the ground may not even distinguish the sound from background noise, one question NASA wants to answer with its Galveston tests is whether the agency needs to text residents after a flight to prompt them to fill out a survey response, says Jonathan Rathsam, a NASA research engineer at Langley.
NASA will fly two F/A-18s — one serving mainly as a spare — out of nearby Ellington Airport. The planes re-create the low-boom noises by diving from 50,000 feet, hitting supersonic velocity briefly at 40,000 feet and leveling out at 30,000 feet. NASA plans to create one to eight sounds per test day, with about 14 test days over a three-week period. By creating the sonic booms 40 kilometers off shore, the sounds will be softened by the time they reach the ears of Galveston residents. While NASA won’t notify onshore Galveston of the specific test days ahead of time, it will give a heads up to the maritime community because boats and ships below the F/A-18s will hear normal supersonic booms, akin to the sound of a clap of thunder directly overhead, Coen says.