I had a recent event that sounds similar: Fuel pump - it was fairly loud and
from the back seat area. I ran some injector cleaner and dry gas through it and
haven't hear a peep since (6months). I think it was ice crystals???.
If it is your fuel pump - and you can't remedy it with a "cleaning" its big
Your car is fairly new - may be a flukey abs sensor, or even the little fan that
sucks in the air from the cabin to check temp (my 1990 little motor has bad
bearings now and I hear it every morning).
Good luck - let us know what you find..