在網頁裡有提到了
LD3520 1.U7
RIPLOCK REMOVED for fast DVD ripping

LD3520 1.U7 QUIET
RIPLOCK enabled for quiet DVD playback on your PC. Please note, this will only playback slow on pressed DVD’s. DVD-R and +R media will still play at full drive speed. This is a feature of the STOCK NEC firmware.

Quiet的話，讓你在放DVD時會安靜一些(但是不包括-R/+R片喔)