HD vibrating should i worry

[Btone]

i have noticed the the of the 2 Maxtor DiamondMax Plus 10 NCQ 250GB disk i have. one vibrates a LOT more than the other. you can really feel the vibration if you hold it in your hand, and when in a case the noise it makes id deafening to it vibrating the whole case. should i rms it or is it normally for a disk to vibrate as bad as this