DVD Spinning noise normal?

I had a cheap Toshiba DVD which had spinning platter noise noticeable on quiet passages. I bought a used Sony DVD S7000 high end player which does the same thing but not on all disc's.The original owner stated he noticed it also but only on some DVD's. Any reasons why DVD players are super quiet like high end CD players? Thanks
DVD players are increasingly using computer rom drives, which spin faster at times.. so yes, this may be perfectly normal
It could also be that some of your discs are warped, causing them to hit the sides while playing. This tends to happen to discs that are used or left in the car system for a long period of time.
A very basic thing you need to understand about DVD technology is that discs DO NOT spin at a constant speed during reading. When the laser pickup is reading the inner part of the disc near the spindle, the motor spins the disc faster (max speed 500 rpm). As the laser tracks outward toward the edge, the disc is slowed progressively (min speed 200 rpm). So, the speed of the disc varies from 200 to 500 rpm while it is being played. This happens on every DVD; you're only noticing it on some discs.
I have experienced with three DVD players: Sony, Mitsu, and a Panasonic all about 150.00.

The Panasonic appears to have the best built tranport and case - it does a better job of keeping the spinning noise from being too loud.

The Mitsu is very loud. You can hear the disks spin.

The Sony is in between.

My guess, it has to do with the trasport and and case. I end up putting some sound insulation inside my equipment cabinet and small piece of terry cloth under the mitsu..and it soaked up a lot of the noise.