I should have googled before I wrote. This is probably the exact problem I am dealing with and the line at the bottom says it all:
The DVD plays, but the audio is muddy; what do I do?
Most DVD players have several audio modes that change the sound for different purposes. For example “action movie”, “symphony hall”, etc. Using your DVD remote control, find the button that changes the audio mode. Make sure that you are in “normal”, “basic”, or “regular” mode.
>>>>>>>>>Playing an instructional disk with voice narration in another mode can result in very muddy audio.