I just noticed this today, whenever my 360 S (bought it last December) turns on with Black Ops in the drive it makes a really loud buzzing sound during the game identification process.  Likewise it makes the same sound when returning to the dashboard or launching the game.  It's quiet when I play the game (it's installed to the HDD), but whenever it reads the disc it does this.  It doesn't make this sound with ANY other 360 game and I have a few dozen.

Any idea what could be going on?

It happens whether it's vertically or horizontally standing.

Strange that it only happens with Black Ops, but mine makes noise too. It seems to be vibration more than anything else. If you put your hand on the system, the sound should decrease. Maybe try placing it against a wall or something so that it vibrates less. Not sure what else to tell ya.

It's because the disc spinning is loud as hell. Some games are louder than others for whatever reason. S'funny, they fixed the loud-ass fan but the system still sounds like it's blending your disc every time it spins.

" @JJWeatherman: mine is actually louder when it's touching something. I just try to install as many things as I can. "

" I think you're on to something with that vibration thing.  I realized the system was very slightly hanging over the edge of my desk.  I pushed it over a little bit and now it's a lot quieter with Black Ops.  The game is still louder than ME2 or Reach or anything else I play regularly, but it's not as terrible. "

Sometimes it's just the disc. I remember buying a copy of Tiger Woods 09 -- this was before you could install games -- and it would make some god-awful grinding noise whenever  I played. I took it back to EB the next day, grabbed a new copy and never heard that horrible noise again.