Hi I have a question

I have a question about voice processing.
I have constructed a voice amplification system (microphone - codec - earphones).
The voices from television or radio are clear.
But when I talk to a friend, my friend and my voice are not clean.
I don’t know why.
Please, what is the reason?

Thank you.

It’s hard to troubleshoot your problem without knowing more about the setup.
What specific hardware are you using?
What is the physical setup?
What is the code? Please provide a link.

I have a link with hearing aid supplies maybe it’s gonna be useful for you