Yáʼátʼééh! I think the course is still in an early stage. And the Duo Team has already said the the audio will be added with more advanced skills. I really hope that the course will be updated soon. :)
Note: Sorry, but I really do not know if you were replying some comment here, or something like that. I just wanted to remark the info by the Duo Team.
I hope it helps. ;)