Low frequency noise since update - MBP

I have a 2 year old MBP. I just did the most recent update, OSX update and other stuff. Ever since then, I have had a low humming sound coming from around the right side of the computer. Possible a fan. Not sure, but it didn't do it until the update, and now its a rather annoying sound. I most definitely would have picked up on it before.

Any ideas, or other people with same complaints? Thanks!

Update and bump:

All the searching I can find only addresses the late 08 models, unibody. But I did the recs I could find by resetting the SMC and PRAM. Noise still there. Any other recommendations. I am not against taking this bad lad apart!

Still having this issue, just wanted to bump the thread.

Edit: Actually, through closer listening, it does sound more intense when I put my hear to the aluminum on the bottom left corner, so the HDD I suppose. Any other people with similar noises since the last big update?