Can you hear me now?

More simple bite size tat for you.

Have you ever been in a situation where, when on the phone, you can't hear the other person because of a room full of cunts who won't shut up or other such annoying background noise? You probably do what everyone else does and put one finger in your free ear to block out the noise. This never really works and the reason for that is that most cell phones and just about all land lines are "full duplex".

This means that the signal you hear in the ear piece is mixed with your own voice from the mouth piece - and by extension all the background noise too.

Phones were designed like this because the engineers of the time believed that if they mixed in the sound of the callers own voice into a conversation said conversation would sound more "realistic".

So, if you want to hear someone better on the phone, cover the mouth piece. This stops the above from happening and creates what is called the "cocktail party effect".
Yes, you'll still hear the cunts speaking inane nonsense in one ear but your brain can now block that out. Like when you're at a party and the room's full of separate conversations but you can focus on the one you're involved in.

A simple sketch of this is...

Voice - left ear - BRAIN - right ear - room noise.

And when on a phone with an uncovered mouth piece it goes like this...

Voice with distored room noise - left ear - BRAIN - right ear - room noise.

That's harder for your brain to unmix.