Some commenters say they hear better with eyes closed. I find that repetition also helps. I repeat the audio over and over again until I start to hear the pronunciation. If I still can’t hear it after 3 to 5 times, I look for the pronunciation elsewhere or move on and make a mental note to find another pronunciation in a later DL lesson.
Since different pronunciations exist in real life, I am grateful for the variable pronunciations we learn in DL.
It took me about 60 to 100 hours of DL before I started to hear the pronunciations that the diacritical marks, diphthongs, and spellings convey. The more I study, the more I learn.(I have not yet figured out how to convey the difference between these two meanings of học. Also as in, I study but I do not learn.)