Since this was brought up in another thread and then dropped, I'm starting its own thread.
I am a musician by training and so I often "hear" aircraft before I would otherwise recognize them -- or I can have my back turned and still know what's taking off behind me.
Here are my descriptions:
(Anything piston-engined) -- loud motorcycle (gee, I wonder why??
ERJ-135/145 -- High-pitched whine
Airbus-320 -- Hairdryer on "air" setting
Airbus-310 -- Gale force wind
Boeing 737-200 -- Tin foil snapping within a loud roar
Boeing 757 -- Whoosh going to roar (on takeoff)
Fokker-100 -- Hairdryer on "high" setting
Anyone else want to jump in?