I have a new 2006 Elantra GLS with only 675 miles, which has developed
its first (seemingly) abnormal noise. I say "seemingly," because
perhaps it's normal. I plan on taking it in to the dealer for a
listen, but also thought I would post it here in case anyone
(Hyundaitech?) may have any ideas.

The noise appears to occur when the engine is at operational temp, and
is most noticeable from around 1900 to 2100 RPM. The noise is present
at in Park or Neutral, or when driving at those RPM ranges.

I wish I would include a audio file, but it sounds kind of like a low
to mid-pitched "rrrrrrr" with a lower-pitched rumble (almost like a bad
bearing). It's coming from the crankshaft and accessory belt drive side
of the engine (left-side when facing the car). I spent some time with
a mechanic's stethoscope this evening, and couldn't come up with
anything localized or definite. I do know it's coming from the
bottom-half area of the timing belt cover area, but it's really hard to
pinpoint the source.

I know it could be anything, but is it normal for the timing belt
tensioner to make some noise? If not, and if it's the timing belt
tensioner, do they prematurely (infant mortality) fail occasionally?
Another possible source may be the AC belt tensioner, below the AC
compressor. Or, possibly even the alternator bearing. I know I'm
grabbing at straws here, but it certainly doesn't sound normal, and
neither my wife or I have heard it until today, as the car makes more
noise even at idle than before.

The only thing that I've ever heard even close to the "rrrrrrr" sound
is what some of the GM X-series (Celebrity, 6000, Cutlass Ciera, etc.)
cars used to sound like from inside the cabin, and I think that sound
was transaxle related.

Obviously, it's off to the dealer for some troubleshooting. I just
hope the tech can hear it . . .