The headphones were attached to rails on the ceiling of the classroom. The French teacher lowered them and while we were holding our breath, we each took a headphone: we had a French listening test.

Nobody was comfortable, everyone knew: I can't do this. It goes too fast, I don't know many of the words, I don't understand the questions I need to answer.

Do you recognize this feeling from your language classes? And as a student there is nothing you can do about it; a listening test like this is simply unsuitable for learning a language.

At moments like these there is a cognitive overload in the student's brain; the working memory is overloaded with input. What kind of overload are we dealing with?

First of all, many of the words in the input are unknown or not well acquired. The working memory tries to give meaning to each incoming sound. It does that by searching for meaning in the long-term memory. That takes time, especially when it's trying to find information that is not even in the long-term memory yet. Meanwhile the listening test continues, and more words have entered the working memory that need to be processed.

The working memory has a capacity of about 5 to 7 items. Just take a look at how many items are in that listening exercise and the speed with which they are given to the listener. Then you will hopefully understand that the working memory simply cannot process all of this.

Research shows that a minimum of 95% of words in a text need to be comprehensible to the reader in order to read and understand the text. With a listening exercise this % might need to be higher, as you don't get the chance to go back to the input, like you can with a text. 

Input that you listen to is transient; the working memory holds it for about 2 seconds and f then it's gone, because there is more input coming. During a listening exercise a lot of the input is forgotten. I remember that, despite my concentration and effort, I was not able to recall what the listening test was about when I left the classroom. That's because a lot of the given input is not remembered. So even though students might have answered some questions correctly, little will have been learned from the input; little of the input has been processed and forwarded to the long-term memory. it really goes in one ear and comes out the other ear. 

So, what to do as a teacher? You can play the listening test various times and each time focus on a different exercise. The first time your students listen for overall understanding of the input; what's this about? Another time they listen to focus on specific details: the speaker mentions 3 advantages of this product, what advantages are there? Another time they listen with a focus on a specific word or structure; the speaker says X, what does the speaker mean by this? And let your students listen while they read the transcription and then answer questions.
Spread all this over several lessons and then assess (formative or summative) all of these exercises. (thanks to Gianfranco Conti and Steve Smith, 2019).