Apple PowerBook G3 - Manual (Page 20)

4 Push the tray in to close it.
When the CD-ROM drive is in use, you may notice some vibration and noise
as the compact disc spins rapidly. Certain discs can cause the drive to vibrate
because they have heavily inked artwork or a label that creates an imbalance.
Variations in speed of CDs is normal. Different types of disks run at different
speeds; for example, audio CDs all run at a low speed.
The high-speed CD-ROM drive for your PowerBook contains an intelligent
sensor that detects an unbalanced disc and adjusts the disc speed to minimize
vibration. Even when the speed changes, the CD still functions normally, but
it may transfer information at a somewhat slower rate.
Some vibration is not unusual for a high-speed CD-ROM drive, in part
because there is no specification for balance of compact discs. To minimize
vibration from unbalanced compact discs, do not put labels on your CDs.
Place the computer on a flat, solid surface when using the CD-ROM drive.
Keep the CD-ROM drive’s tray closed except when loading discs. This
prevents dust from getting inside the mechanism. Also be sure to keep the
CD’s recorded surface (the side opposite the label) free of contamination such
as fingerprints, dust, and grease. The performance of the drive depends on
the optical quality of the CD media.
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