I just got a mid-2012 15" cMBP. I noticed when starting up it seems to have a different chime than I'm used to. It's almost like the volume is up too high that it is making something vibrate. It's not the SuperDrive noise. Just wondering if this is normal on this model...it works fine, and if it is vibrating I don't know what it could be...nothing seems loose. ---------- I only notice it because my mid-2009 doesn't sound the same.