Effective listening is all about how well the listener could understand the content through listening.
Lets take a look at what affects our listening.
Noise level, clarity, speed, accent to name a few .
Once we overcome the speed issue,
we should be able to grasp most of what we are listening to.
However, it is also hard to train our ears to catch every single words we are listening.
The trick here is to only sample what we heard and try to make up the complete sentence by constructing it behind our brain to form a complete picture.
We could experiment this in a lab and use the same method to help us improve our listening.
A demo as below:-
T..... fox j ...the wall .....
Since we had " fox" and " wall" we try to guess what the fox do with the wall.
Most of you would guessed " fox jumped .... the wall"
If could improve the skill of sampling what you are listening.
It will come no surprise that you have understand better even if speed, clarity or accent has affected your hearing at the begining.
Technically, this is how we could overcome poor listening.