Two new projects aim at reducing the noise of Unmanned Aerial Vehicles, or UAVs. First, a team at Georgia Tech has analyzed the acoustic signature of piston engines of their own and a number of US military UAVs using in-flight and ground based tests. Their goal is to use acoustic signature control to make low flying UAVs less detectable and improve the performance of their ground noise monitoring sensors.
Second, a project sponsored by the US Office of Naval Research aims at replacing noisy piston engines with fuel cells. In addition to reducing noise emissions, the new hydrogen-powered fuel cell design is also expected to provide significant improvements over earlier battery-powered designs.
Video of the ION Tiger (wmv)
ION Tiger on IEEE's Automaton