MacBook Pro Retina rattling noise About two months ago, I purchased a MacBook Pro Retina, 13-inch (model MF840LL). Recently, I have noticed a quiet rattling noise when doing something performance-intensive (some webpages in Firefox, for example).

What is causing this, and what should I do about this (if anything)?

I also have a Speck seethru case on the computer - could the case be rattling against the computer?
Assuming your case is not the cause of the rattling issue (in other words take it off for a while and see) then this is an issue that should be brought to the attention of an Apple Store Genius near you.

The days of computers, especially laptops, making any kind of noise (barring the occasional optical drive seek noise...) is long over.

The Mac is still (essentially) brand new and under warranty and Apple needs to have a look at it.

Be advised that if they need to send it off for work they will not guarantee data on your HD stays in place. So make sure you have (at a minimum) an up-to-date Time Machine backup. Me, I'd image it (SuperDuper or CCC) just before heading out the door to my Apple Store appointment.