Controlling noise in unmanned aerial vehicles may help them evade enemies

Washington, Jan 24 (ANI): In a new study, aeroacoustics researchers at the Georgia Tech Research Institute (GTRI) are investigating a stealth technology that could help control noise from unmanned aerial vehicles (UAVs), which may help the aircraft to evade enemies.

Recently, UAVs, which are remotely controlled devices, are growing ever more vital to the U.S. armed forces in roles that include surveillance and reconnaissance.

In some instances, UAVs must fly close to their targets to gather data effectively and may evade enemy detection.

Now, aeroacoustics researchers at the GTRI are investigating an additional kind of stealth that could also be vital to these UAVs - technology that can evade enemy ears.

"With missions changing, and many vehicles flying at lower altitudes, the acoustic signature of a tactical UAV has become more and more critical," said senior research engineer Rick Gaeta.

The GTRI investigators' central task has involved characterizing the acoustic signature of a UAV's propulsion system, which typically consists of a piston engine and a propeller but could also be electrically or fuel-cell powered.

To operate the engine without a propeller attached, GTRI investigators had to search for quiet ways to provide both substitute cooling and a load for the engine to spin.

Another complex testing issue involves measuring acoustic performance and engine performance simultaneously - a key to making the right design tradeoffs.

Researchers utilized two special acoustic chambers at GTRI's Cobb County Research Facility - the Anechoic Flight Simulation Facility and the Static Jet Anechoic Facility.

The flight simulation facility is a unique chamber with a 29-inch air duct that can simulate forward-flight velocities while also allowing precise acoustic measurements.

To take full advantage of the flight-simulation chamber, Gaeta's team built a special dynamometer capable of driving a small UAV engine and a propeller.

By placing the engine-dynamometer unit in the simulation chamber, the researchers could test both engine and acoustic performance, thereby providing data for UAV design tradeoffs.

"We have been able to develop a unique testing capability as a result of this project," Gaeta explained. "It allows us to separate acoustics issues into their component parts, and that in turn helps us to attack those problems," he added.

Investigators are also focusing on other issues, such as how to quiet an unmanned aircraft so that its own sound doesn't interfere with the task of monitoring ground noise using airborne sensors.

"Our next step is to put our findings into a prototype for testing," Gaeta said. "We believe that we have the means to make tactical UAVs much quieter," he added. (ANI)