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USA: Quiet planes make good neighbors

Can airplanes be quiet? Much depends on the answer to that question. Internal combustion engines are inherently noisy and propellers add to that noise by their speed of rotation, the thrust-load they bear at takeoff and, most annoying, the explosive air produced by blade tips nearing the sound barrier. Pilots who link the healthy sound of an engine to their personal safety are, at least in part, proofed against offense, while non-fliers, even passengers, cannot be expected to enjoy the outburst. For those who live near airports, however, the constant drone-to-roar of engines can be offensive, even frightening.

Just like the mechanic says when your broken car needs more sleuthing: we’re working on it. In fact, the challenge of sustainable air-travel is being worked on by some of the brightest minds on the planet. About 200 of them gathered in Santa Rosa April 27, 28 for the 6th annual Electric Aircraft Symposium. The silent flight revolution is in its 6th year!

In a talk entitled “Quiet Propulsion for Small Electric Aircraft” Krish J. Ahuja, Regents Professor at Georgia Institute of Technology School of Aerospace Engineering, explained that a typical neighborhood has an ambient noise level of 60-65 dBa and that propeller sounds would need to be 12 dBa lower (48-53 dBa) to be masked into the background. Dr. Ahuja: “Since decibels are measured on a logarithmic scale and 3 dBa represents a doubling of sound pressure, this would be four orders of magnitude lower than normal street noise.”

I’m not sure what that means either, but isn’t it good to know the Science of Noise is progressing along with our national noise-making.

Cafe Foundation of Santa Rosa
Qualifications narrowed the GFC field from thirteen entrants to four. (One team was demoted to “exhibition” when they ran out of time to install the required ballistic recovery parachute system.) The green machine finalists departed the 170mile round trip from CAFE Foundation’s Flight Test Center at Sonoma County Airport.


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