Why do some cd-roms make a lot of noise?

[techs]

I work with a lot of computers. There is a big difference in how much noise a cd-rom drive makes when it reads disks. Even on the ones that are quite some disks will run quiet and others will make a lot of noise.
I am guessing it is due to disks that are not balanced?
Or is it something else?
Anyone have the scoop on this?
Thanks

 

[natto fire]

That is correct. Because of the rotational speed needed to achieve the upper (32x and up) speeds, balance comes into play a lot. Another factor is how well the drive is designed to absorb vibration from improperly balanced discs.