Hello,
If your audio is actually in Breeze, you can easily go to the
Breeze menu, and then go to Audio Editor, and edit the volume right
in there. You may be able to modify the viewer.xml, but having some
knowledge with customizing that file, I have yet to come across it
myself. If you could somehow import your audio files onto the
corresponding slide, you can edit the volume in the Audio editor, I
believe its under Tools --> Volume.
I hope this helps
Doug