Use 32 kbps mono mp3 for spoken word files. While wma at 32 kbps sounds better than mp3 at 32 kbps, with wma battery life is probably around 20% shorter, so it isn’t worth it. Using variable bitrate for spoken word files isn’t worth it though, as the space savings will be quite small(32 kbps is small enough) or the quality improvement won’t be much. With VBR, often the elapsed time counter won’t work properly(especially with longer files), and there is a much greater chance of playback glitches than with a constant bitrate.
I have downloaded many lectures that were at bitrates from 16 to 64 kbps mp3. Even many of the 16 kbps ones sounded decent, but the 32 kbps mono ones sounded noticeably better. The ones at 64 kbps really didn’t sound much better than the 32 kbps mono ones.
