MacBook Pro makes a scratching noise?
I've had this problem as well an posted this question which is very similar yours.

Here's my solution:

On the whole logic board you'll find tiny elastic sticks. They can be pushed a little. These sticks hold the aluminum bottom off the logic board and cause the disturbing mechanic noises that your are talking about.

Do not take any chances and apply insulating tape on every place of the aluminum bottom that the sticks can contact. Apply the tape again as it easily wears out.

Now, the Macbook Pro does not make any of the previous noises anymore.  It feels like a solid aluminum brick on my lap.



And a close up...



This is what the back cover looked like when I was done. Uh, it's ugly! I'm glad it's on the inside.