I got my parents a Pioneer 105S, and it is unbelievably loud. I mean, 40dBA or more. It sounds like a portable air conditioner. When playing DivX movies, I have to literally stick a sock in it - I plug the hole with my foot.
However, my friend has a 105S or 106S, and it is of normal noisiness you would expect from any modern day CD-ROM or DVD-ROM. Let's face facts, any drive going full tilt will be loud. Cds and DVDs aren't played a full speed, so theoretically should be quieter. I dunno, maybe my parents' drive is flukey, but just so you know.
Scootin, you mentioned something about a sound cover - is this an actual product? You've piqued my interest.