The first example is obviously that of a child who wants to use the toilet. You can almost hear that whining right next to you, and feel that desire to slap someone.
The second example is obviously that of a stereotypical “gangsta.” Can’t you feel that air of danger, and imagine that gun pointed at your head as he looks away to talk into his phone like it’s a walkie-talkie?
The third example is simply someone who is hyperactive. No real structure involved, all capital letters: they’re obviously excited for their soup.
There aren’t a lot of ways to fix a voice, besides practice and trial & error. If a voice does not sound quite right for what is to be delivered, try experimenting with different words in order to deliver the right feeling.
A good way to see if a voice is coming out right, is to speak what you are about to write the way you would want it to be heard for it’s purpose. Then, once you’ve gotten the actual hearing down, write the words you’ve spoken with the correct tone and emphasis you need, and you should have the right voice.
You really should not be hearing other voices in your head. If you’re hearing voices in your head, or have a multiple personality disorder that is causing you many problems and making you wake up next to strangers in a different town, you may wish to seek a psychologist.