If it helps, remember that vowels with Umlauten are always stressed, not just in the stressed syllable but also the stressed vowel in a diphthong. This doesn't interfere with interpreting ‘äu’ as the same as ‘eu’, but it means that you can't interpret ‘iä’ as the same as ‘ie’.
Unless it's changed since then, I think vowels might yet be involved. I can kind of hear an L, I think, but only if I allow a different sound for the second vowel. In this word, the Ä makes a long vowel sound; if you hear the L, you get the L followed by a short vowel sound. At least, that's what it is for me. Since I expect the long vowel, the interpretation with the L is difficult for me to even hear.
Then again, it may be that the audio has changed in the past three years, and it used to be that there really was an L there. I don't know.
I would like to work on my vocab. without having speakers on. Sometimes it endlessly asks me to say the word or spell it and when I say 'skip it' the green bar disappears. On my phone it says it will turn off the microphone off for an hour. I'd like to have that option on the computer.
How did you report it? Through the bug report form https://support.duolingo.com/hc/en-us/articles/204728264-How-do-I-report-a-bug- ?
Or from inside the app / web page with "audio is bad"? The latter is useless, because it just reaches course contributors who can't do anything about it.