Originally Posted by
pax britanica
It always amazes me how turbo props make so much noise up at FL200 and more
Used to live in The Wirral, close to the WAL VOR, around 1970, and BEA Vanguards on Heathrow-Belfast were commonly audible when at altitude. The Vanguard was a real noise maker, it is surprising nothing was ever done about it. I suspect the square-cornered prop tips. I recall more than once being up Arthur's Seat in Edinburgh, the small mountain to the east of the city centre, and hearing them manoeuvring, not even airborne, at Turnhouse, about 8 miles west.
A fainter noise from small childhood, around 1958-60, in Somerset, was a late night droning, which at that age in a darkened bedroom I regarded as somewhat eerie, which would last for several minutes, gradually fading away. I now believe it was DC7s and Constellations from Continental Europe heading for Shannon and a westbound Atlantic crossing.