At the moment, I am doing some work on misunderstandings in conversational speech, specifically to try and work out what features of pronunciation result in loss of intelligbility and which ones do not matter so much. If we can determine this, we can help teachers to know what they should focus on. Some sounds are more important than others, and it is important for learners to know which are the most important.
One would think that context can help resolve most issues, and indeed it usually can. But sometimes even in context one gets confused. And occasionally this confusion can be quite surprising.
When I was at Guangxi University in Nanning, I recorded lots of students talking to me. One of the questions I asked is, "What do your parents do?" One of the students told me that her parents sell flutes; and it took me quite a while to work out that they actually sell fruit, not flutes. Initially, I visualised them selling bamboo musical instruments to tourists or something like that.
Afterwards, I felt really stupid, as I know full well that [l] and [r] tend to get confused in word-initial consonant clusters in the English spoken in south China; but this is the kind of misunderstanding that is common for listeners. And it is valuable for speakers to realise that distinguishing [fl] from [fr] at the start of a word is important.