I Came, I Saw, I Learned...: Adobe Captivate 5: Make Quick Work Out of Adding Audio to a Project
Tips for streamlining the process of adding multiple audio files to Captivate
elearninglive.com » Captivate Audio Output Settings Comparison - Part One - Encoding Bitrate
Results of an experiment on the encoding bitrate for Captivate. Mark Siegriest is trying to find the best audio settings to balance sound quality and file size.
The most surprising finding in this is that at the lowest bitrates, the file size actually went up, not down. 32kbps was the smallest file size in his sampling.
So basically from what I can see there is no point in ever going below 32kbps as you’re gaining filesize and losing quality.