Audio Quality Horrible when Previewing or Publishing

I have recorded narration directly into slides and also studio produced narration inserted as a file. When I preview just the audio track, the quality is great. When published or in preview, the quality changes to a "tin can". I read to try changing compression to "none", however it is locked at Automatic and doesn't allow me to change. 

Text to Speech audio allows me to change the compression. Why not a recorded file??

Please advise.

Cris