noisy BD-R

[mickmars]

Hi All
This is probably a bit of a basic question for this thread, but...
I have been putting 2gb mkv files on a "cost effective" bd-r disc and when I put in my bluray player, they play fine but the disc spinning noise is really loud.
Putting the same files on a Verbatim bd-r works just fine, So I'm wondering what it is about the cheaper discs that makes them so noisy ?

thanks

[CDK]

just a curved plate