DT Videolabs PlaybackPro - Manual (Page 12)

Set Alert Volume to zero
Uncheck: Play user interface sound effects
Uncheck: Play feedback when volume is changed
Set Output Volume to full.
CDs and DVDs: Set everything to Ignore
Although it is not in System Preferences, it’s best to unmount any network shares
before going into show.
PlaybackPro User Guide
Page 11
Sound
CDs and DVDs