Sounds nothing at all like a diesel.
First thing you hear are the compressor sounds. When it starts moving you hear the low-pitched growl/whine of traction motors. When moving at speed, this seems to fade as the loco sounds are drowned out by the sounds from wheels/track, rolling passenger cars, etc.
The engine itself seems to glide by silently just as the real ones did. The horn is the sound of an air horn, just as I also remember from hours spent at NYC trackside.
Overall, the sounds remind me of what a ride on a subway sounds like from inside the car.
Did anybody catch the fact that the engineer sits in the #2 cab, and the engine starts up with cab #2 forward? Prototype photos show that little attempt was made to run the engines with the #1 cab (marked F) in the lead, so there is nothing at all wrong with this - just interesting.
Overall, a great little engine. 
Will try to shoot some video soon.
Jim
