The mesh can be dl'ed at avsim, just look in the FS2004 section and use the author's name 'Pietro Mauri'. For the Alps you'll need Germany, France and Italy (his country). It's in the readme's.

Much more mesh for 2004 there, it is a dream  8)

The sound, well, hard to describe it has a specific whining to it, like as if from the bearings in the rotorhead.
I'll try this one here (3 of 3): http://www.simviation.com/fs2002heli25.htm

Edit:/ tested the sounds from the above link, the 'AT3inside.wav' has the high pitched sound, very specific, but listen around the noise that is included as well. The 'AT3outside' has the distinctive sound in the back, though it's difficult to make out. If you filter the noisy jetflow, you'll hopefully hear it.