Alphabet and proninciation
Are there somewhere the alphabet and the rules of pronunciation?
The tips and notes in some lessons will help you with this, but there is a master-list with audio samples here: https://www.kli.org/about-klingon/sounds-of-klingon/
There is a Skill a little bit into the course which teaches the names of the Klingon letters and has a description of the pronunciations in the Tips & Notes, however, that skill also lacks audio.
If you want to check out some additional ideas for learning the pronunciation, check out the thread at: https://forum.duolingo.com/comment/26605745
If you want to read about the other known issues in this course, read the post at: https://forum.duolingo.com/comment/26778885
And finally, the only way I know of to complain to the administration about the lack of audio on this course is to file a bug report: https://support.duolingo.com/hc/en-us/articles/204728264-How-do-I-report-a-bug-