Complex being built to map aircraft sound

By DREW HAMILTON, ATECSeptember 11, 2008

The future of military and civilian aircraft will be a silent one with the construction of the Aeroacoustic Research Complex on White Sands Missile Range, N.M.

The one of a kind complex will be used to map sound being emanated from aircraft in flight. The sound data collected can then be used to design quieter aircraft to gain military advantages.

The complex is composed of an array of microphones both on the ground and mounted on a pair of 300-foot tall towers currently under construction.

Test aircraft will fly between the towers, enabling acoustic data to be collected and evaluated. The information will then be used to attempt to identify methods of reducing the sound being emitted by the aircraft.

While the complex will initially only be able to evaluate small aircraft, such as helicopters, light fixed wing, and UAVs, plans have already been approved to construct a larger set of towers to enable the testing of larger aircraft.

"Eventually [we'll be able to test] any kind of platform you can think of, cargo, commercial, anything," said 2nd Lt. Boyce Dauby, a project engineer with WSMR's detachment of the 46th Test Group.

The ARC will be ready to begin testing as early as September.

What makes the complex unique is that unlike other aeroacoustic facilities, the ARC will be able to map the data out in three dimensions. While 2D mapping facilities already exist, the 3D data mapping that the ARC will be capable of will allow for more advanced and accurate data collection.

"Noise propagates in every direction and you can't do the kind of [data collection] we want to do with a 2D system," Dauby said.

WSMR's controlled airspace and large open ranges made it an ideal location for the ARC.

"You have to ensure that you have a quiet zone around the measurement site. Any noise encroaching on the test can contaminate the data," said John Hall, ARC project leader from the Air Force Research Laboratory. Hall said that WSMR's quiet natural background has made it a location to perform acoustical experiments in the past, and it's controlled airspace and ranges ensures that testing won't be disrupted by other activities.

The benefits of quieter aircraft aren't limited to the battlefield; many airbases and airfields around the world are located near civilian populations. Encroachment of civilian communities and developments can result in noise complaints and limit training opportunities. Reducing the noise emitted by military aircraft will allow U.S. air assets to operate and train near civilian populations while minimizing complaints.

The ARC's capabilities will also be attractive to commercial industry as there is a great deal of interest in noise reduction from civilian aircraft manufacturers. "We've already been approached by a lot of aerospace corporations, both on the engine and airframe side... because it's a big selling point in commercial aviation if you can mitigate noise --- complaints," Hall said.

As a dual use facility, civilian companies can run experiments and collect data to help the development of quieter private and commercial aircraft.

According to Micah Downing, chief scientist from Blue Ridge Research and Consulting, an acoustical firm supporting the ARC, densely populated regions like Europe have stronger environmental regulations and a greater need to limit noise pollution.

AFRL has partnered with NASA on this project through an Interagency Agreement to share the investment. AFRL would like to thank Detachment 1 of the 46th Test Group as the Air Force sponsor of the ARC, WSMR's Business Development Office and WSMR's environmental division for their help in the approval process.

"A big milestone was the approval of the environmental assessment," Hall said.