On a B777-200 aircraft to Guam, while sitting in the air strip I am measuring around 68 db per 1/3 octave band across the 6.3-20 Hz infrasound range, with all plane doors closed and air conditioning on. There was 6 db drop when AC went off temporarily. Sound levels were fairly steady, and I will concentrate on 10 Hz band levels for simplicity. Motoring on the ground and liftoff had highest levels, 90-100 db, ramping down to 72-77 db range on ascent and holding steady when we reached cruising altitude. The highest level reached during flight was 92 dB in the 40 Hz band, where there was a discrete peak. It's a bit of a challenge to make the measurements without freaking my fellow passers out or alarming the flight attendants. I walked around with the meter to see how homogeneous the levels were during the flight, and even in the bathroom the pressure levels were fairly even. The pressure levels during descent felt about the same. A dash through Guam to the next flight to Koror, which had a smaller plane and palpably lower ambient noise levels. There was no way to make these measurements discretely in this small plan, but it was my impression that that flight's sound had lower levels and a higher pitch.
Late arrival on Palau, and back up at 4 AM after a few good hours of sleep. I am at peace with sleeping only ~4 hours when on work travel, this is how my body responds to stress. That, and a ravenous appetite - eagerly waiting for breakfast.
Light breeze, maybe 1 m/s, ambient noise levels at 10 Hz fluctuating around 50-60 dB levels, depending on the wind gusts. Food is out, time to grind!