Hi all! 

Ive seen others post questions with introductions, so hopefully this is ok here.  If not, Ill be happy to move it or create a new thread!

I just bought a Polar Express set, the new one with Bluetooth control, which is pretty cool. 
My question is, with the chuffing on, and no other movement/sounds, there is a somewhat "static" type sound as well. 
When I turn chuffing off, its quiet, and when other sounds are played, there doesnt seem to be any additional "static" sound. 

Originally, I thought it may be a problem, as I read that sometimes the chips in the board can get slightly dislodged, but beyond that, could this just be a normal sound?  Maybe steam escaping or something? 

The whole on-board sounds thing is completely new to me, as Im used to just my old O-gauge set from the 50s. 


EDIT:
So earlier today (Monday, Dec 2), I was able to find a video, two actually, of the same engine, and they both sound the same as mine. 
My best guess is that this sound is to approximate steam escaping constantly.   
Incidentally, there do not appear to be removable "chips" in this version as in some others, possibly due to this being an entry level locomotive, vs a higher end model.