Acoustic testing conducted with NASA has confirmed the low noise levels of Joby’s eVTOL aircraft.
Joby’s piloted five-seat eVTOL aircraft can carry four passengers at speeds of up to 200 mph (320 km/h), with a maximum range of 150 miles (240 km) on a single charge. The eVTOL aircraft has been in development for 10 years and the company has completed over a thousand flight tests have been completed.
Joby plans to launch its eVTOL aircraft in 2024.
The acoustic tests were done with the California, USA-based company’s full-size pre-production aircraft during two weeks as part of NASA’s Advanced Air Mobility National Campaign.
The aircraft registered the equivalent of 45.2 dBA from an altitude of 1,640ft at 115 mph (185 km/h), a sound level which Joby believes “will barely be perceptible against the ambient environment of cities”.
NASA engineers also measured the aircraft’s acoustic profile during take-off and landing to be below 65 dBA, a noise level comparable to normal conversation, at a distance of 330ft (100m ) from the flight path.
JoeBen Bevirt, founder and CEO of Joby said, “We’re thrilled to show the world just how quiet our aircraft is by working with NASA to take these measurements.
“With an aircraft this quiet, we have the opportunity to completely rethink how we live and travel today, helping to make flight an everyday reality in and around cities. It’s a game-changer.”
All measurements were conducted using NASA’s Mobile Acoustics Facility, with more than 50 pressure ground-plate microphones placed in a grid array at Joby’s Electric Flight Base near Big Sur, California.
To measure the Joby aircraft’s acoustic footprint during overhead flight, it flew over the grid array six times at an airspeed of 115 mph and a low altitude to measure as much of the aircraft’s noise above the background ambience as possible.
Data recorded from the field of omni-directional microphones was then processed by NASA into an “acoustic hemisphere,” representing the sound emission in all directions below the aircraft at a 100ft radius. Joby then applied standard processing techniques for spherical spreading and atmospheric attenuation, resulting in an average free-field overhead flight acoustic reading of 45.2 dBA at 1,640ft.
Joby also conducted more than 20 take-off and landing tests above the grid array, using a variety of acceleration rates and climb angles to allow NASA to capture acoustics representative of likely operational procedures. This data will be used to adjust flight software and take-off and landing procedures for further low-noise optimization.
According to Joby the number of propellers and blades, blade shape and radius, tip speeds, and disk loading of the aircraft have been selected to minimize its acoustic footprint . Each of the six propellers can individually adjust its tilt, rotational speed, and blade pitch to avoid blade-vortex interactions that contribute to the acoustic footprint of traditional helicopters.
More details regarding procedures and measurements will be released by both Joby and NASA in technical papers to be presented at industry conferences this summer.