I know, I know. I need to add some actual updates.

For now, the best way we have found to ensure the mp3's are read by the badge is using audacity to convert the original audio flies to mp3s using:

320 kbps

48k sample rate

constant bit rate

This doesn't mean other options won't work, this is just what we have had the best luck with. It's easy enough to copy any mp3 onto the SD card and try it, right?

p.s. 

Sometimes, if the batteries are running out, it might freeze, so it might not be an incompatible mp3.