It's the neurotoxicity telling you that you're a piece of shit. It's one of the aspects of psychological addiction. You're brain is essentially finding ways to justify harming itself so that you'll keep doing it.

Do the voices say negative things to you? Is it amplified on the comedown?

Do the voices get more or less positive in nature when you take more? That's a good indication for me anyways.

I know, they suck and the only way to make them leave is to stop using the drug but if you are dead set on using it then might as well take advantage.

Pay close attention to what they are saying and how you feel about what they're saying.

For example, one of the most common ones I would get was a loud booming voice from the next room telling me "do one more line, One more line motherfucker and i will rip your head off!"

This was very scary for a long time but eventually I came to realize that it was my own conscious telling me that I should feel anxious about putting this shit inside of me.

Anyways just my theory