Oddly enough 747Focal, still stage three...and worked
good. 
Was staying with a friend some years ago at Morfelden (sp?) just south of the FRA airport, and they had a dB meter just up the street, with a recorder and timer.
B747 departed...full scale
DC-10, likewise, 3/4 scale...ugh!
L1011....supremely quiet, meter barely moved.
LOCKHEED got it right (with proper British engines, of course)...sadly they didn't sell more
