Are you saying that there is no way for me to achieve my stated objective?
It would appear that changes between the 2007 and 2010 version as shown in that YouTube video in post 10 are indeed interfering with what you would like to accomplish.
That’s unfortunate that the audio quality is nolonger adjustable in 2010 (or 2013).
Something you could consider is recording the audio to a separate file while going through your presentation. Save the presentation as a silent video file. Use Microsoft Movie Maker to append the audio to the presentation video.
Microsoft Movie Maker:
http://windows.microsoft.com/en-US/windows7/products/features/movie-maker