Had another posting about this where I had the error "file not found" in the MRL log when giving commands to MRL. I assume this was a timing problem, the audrey file was not ready at the time the playback started.
There is also the fact that raspi 2 by default has no MPEG 2 licence. You can buy it in the raspi shop for 2 pounds, so only a small fee. Unforturnately this however did not solve my sound problems.
Converted then all audrey files to MPEG 1 format using WinFF. This helped to make all audrey files audible using mpg123.
During my OpenCV session with Alessandro I asked him whether he could help me with this issue too. He tried to play a .wav file and a .mp3 files through the audio service of MRL. Both files gave no sound through MRL but worked with mpg123.
I have a Daffodil sound stick for speakers and microphone. I have modified my alsa-base.conf file to have the snd-usb-audio at index 0 and the snd_bcm2835 at index 1.
The micophone works (I can see the in the MRL log the confirmations for the words I say) but playing the file does not throw an error - just does no sound output.