Internal macbook noise ?!

hi i have the latest mbp 15'' 2.4 Ghz, so i was using it on bed and i wanted to fix my sitting position, so i hold the macbook and i heard a noise... i re-shaked the macbook and nothing came out! i made sure that the sound isn't fom the keyboard keys since they're soo solid in their place! i re-shaked it again and i heard the noise again ! and it's coming from the side where u enter your DvD/CD ! is that normal? thank you!

 

haha yeah i did.. btw where can i find the settings for the sudden motion sensor? thx 4 the reply