I know that I am not the only person out here who is having a problem with the clarity of audio recordings. I have seen this issue mentioned several times. The problem is that the voices are simply not as clear in some cases as humans and especially word endings are getting garbled. If I can't hear the words correctly, I also can't write them out correctly. please consider some modification to sound quality.
I see German and French in your stream and I'm quite surprised to see complaints on these voices. As for me, they are amazingly good for text-to-speech. For a long time I even thought they were recorded by real people, until I met some odd intonations and pronunciations.
"Slower down" button usually works fine. There are a few words (like "royal" in German, lol) that are pronounced very poorly, but you get used to them after the first time.
I also found that the endings problems go away when you acquire a deeper understanding of grammar. If I know that "der" changes to "den" in the accusative case, I don't struggle to hear the ending, I know what it should be. Practice more and try to figure out the grammar before typing. Use the slower down button to be sure.
I have found that the speech is generally surprisingly good, except some endings (in Spanish). Thus it is not always clear whether, say 'ellas' or 'ellos' is said. When doing a timed practice, there simply is no time to listen to the slow version - as by the end of the slow version you're out of time anyway - and it is irritating to get the sentence right except for gender especially if one is on a good run!
gustav46's topic says it was posted 2 years ago. I just started using Duolingo for Portuguese, and I find myself experiencing the same garbled audio problem. It is very discouraging that nothing seems to have been done to address the issue. I love the idea of free language learning, but am considering that I might be best served by shelling out some money for the benefit of clearer audio. As others have noted, how can you learn to pronounce a word if you can't clearly hear the pronounciation?