Although electric vertical takeoff and landing (evtol) vehicles are regarded as an efficient solution to resolve future urban traffic congestion, a large number of "air taxi" companies still have many difficulties to overcome - including battery life, fast charging infrastructure, and noise control** Interestingly, Joby aviation has just joined hands with NASA to conduct a mobile acoustic test of its S4 prototype.
The test facility includes a field array of more than 50 microphones to evaluate the noise performance of the evtol vehicle at different altitudes and speeds, and finally create an acoustic model covering all stages of flight.
At present, Joby aviation has disclosed two practical data. First, when the S4 prototype runs at an altitude of 500 meters (1640 feet) and an airspeed of 100 knots (115 mph or 185 km / h), the noise value measured on the ground is about 45.2 dB.
Referring to the decibel chart of common items, this means that the noise of the evtol vehicle is between "refrigerator" and "moderate rainfall" - if used in a noisy urban environment, the noise of the evtol can be basically ignored.
Secondly, during more than 20 take-off and landing tests - when the evtol vehicle rises or falls from a height of 44 meters (144 feet), the noise level measured by Joby aviation at a distance of 100 meters (330 feet) is below 65 DBA.
Referring to the decibel chart, this level is between "normal conversation" and "using toilet / vacuum cleaner".
A Special Message from our CEO and Founder JoeBen Bevirt - Joby Aviation（via）
Finally, given that the noise of the S4 prototype is 45.2 DBA when flying at an altitude of 500 meters and 65 DBA when taking off 100 meters away - such excellent performance is beyond the reach of traditional helicopters based on fuel engines.