scary noises while accelerating on 2000 Nissan Xterra

Just noticed this morning that my car intermitendly makes a loud noise (not the screaching belt noise) when I accelerate at any speed. I could not recreate the sound in neutral and pressing the accelerator, it only seemed to happen while in drive. I also noticed it sounded regardless of AC on or off? Any ideas?

2 answers
Could be a differential, drive axle, or wheel bearing/hub issue, among other problems. Best thing to do--take it into a shop immediately to have it diagnosed. Continuing to drive could cause more expensive damage.
One of the bearing is WHIPPED!