Day 2 of the 2011 Green Flight Challenge had actual flying; very quiet flying. One criterion of the Challenge was a sound check, measuring the low noise levels of the four entrants. Plane and Pilot reported, “Rules enforced a strict noise ceiling to promote the development of quiet, community-friendly general aviation aircraft: “Maximum Noise Limit: Participating aircraft were required to stay below a maximum noise level of 78 dBA during full-power takeoff. (This was a notable goal since Putdue University acknowledged much higher levels for small airplanes, “Flyover levels: A typical single-engine general aviation plane (like a Cessna) flying overhead at 1,000 feet measures roughly 88 dBA, though general averages can drop closer to 65 dB depending on distance, engine power, and altitude. “Comparison: Ground noise from a small plane flyover is comparable to a loud power lawnmower (96 dB) or heavy street traffic (85–90 dB), but it is intermittent and perceived differently depending on proximity to local airfields. “Regulation …
