is noise from commercial aircraft low frequency? I live in DFW about 20min from a major airport and I remember going outside after 9/11 when all air traffic was grounded. It was eerily quiet even though I was still in the middle of a large metropolitan area.
Well it includes those low frequencies. I'm sure if you've flown you've experienced the strange ear-plugging feeling of flight. The fuselage is highly sound damped from the engines but you still get the low frequencies. Also could be that pretty much everyone tried to not go outside during 9/11, probably a lot more than just planes stopped
the air being pushed out/around from aircraft engines probably.
most running engines produce some low freqs, and also slow-rotational things.. like cars' wheels thumping on streets and roughnesses there.. esp. thousands of those. And then combinations of almost same freqs produce very low differentials - something on 50hz and another on 53hz will yield some 3hz. Which cannot be heard, it's to be felt.
Another similar silence happens if one is in a street/ suburb/ block-of-flats full of airconditioners-on-walls when the power goes off.
