This may or may not be considered on point. So, read it with "open ears".

I had to learn Morse Code(MC) for my job years ago. Theoretically, MC is very simple - a single tone active for a given period of time and off for different periods. Space the tones and silence faster of slower and you can code/send more information. (1 period is dit, 3 periods is a dah, the space between characters usually either a dah length or 5 units of time).

Learning MC is usually done at 5 characters per minute. So, you might hear "dit dah (silence) dah dit dit (silence) dah dah dah dah (silence)dit dit dah dit (silence) dah dit dah (that's all actually a meaningless group for characters offered merely for illustration purposes here).

After learning the code, I had to qualify at 18gpm - 18 "groups" of 5 characters each with spaces/silences between groups in 1 minute. Simple math - my qualification was to be able to understand MC at 3x the speed I learned it.

All this leads to my point - ear training. I literally couldn't hear the silences between characters in groups much less those with the characters themselves when I first tried "copying" 18gpm messages. It was all a just an angry muddle screech in my ears. Believe it or not, my instructor turned the speed of transmission up to 25 gpm and had me try to "copy" the code at that speed for about 15 minutes. Of course, I failed horrendously. But when he turned the speed back down to 18gpm, the "transmission" suddenly became clear. I heard all the dits, dots and silences like it was nothing. I was floored.

To me, this is an illustration of what the article suggests. Ears/brains can become accustomed to detecting and processing any sounds in a certain way. Change the situation, and with practice, they can be re-trained. Personally, I've sought out and found online "minimal pair" recordings relating to Russian phonology as that's my target language. Right now, I cannot differentiate between some phonemes.

I couldn't understand much in English like a month or two ago. I can't say that I have the poorest vocabulary, not the richest either, as I could and can read different stories without big problems with understanding them. However, when I turned on a stream of the sound I literally couldn't understand a word. I felt a little bit frustrated, because it turne up to be right that my teacher gave me a C, hardly B in English. I don't know the language. 

Then,I thought: no, it's impossible that I can write and read, and speak (I can, I'd just been hesitating all this time), but I can't understand what they say. So, I turned on the sound again and started concentrating on it. Yeah it was the second try when I understood everything in the audio. The problem was not because I was not understanding anything. The problem was that I didn't try to separate words in the beginning. Then I started separating words, repeating after the speakers and training this part of the language learning. Now I can understand most of the things that I know. Lol

Very good heading. Grabs attention in the context of articles that usually offer advice. 

Useful content. Thanks for sharing.