JamesRx - Yeah, I think I hear it - after I turned my volume up FULL. The sound is very 'faint' (kind of like white noise) and - to me - resembles tiny seeds (or something akin to that) falling on a counter top. A very faint tapping sound.
Having said that, if I owned one of these engines (which I don't) I'm not sure what I'd do about it. With all the trials and tribulations expressed on this Forum these days about getting repairs for more significant things, I'd probably just run the trains and 'try' to ignore it. However, in a perfect world it would be nice if this sound didn't exist I suppose.