My Voice Sounds Robotic After Cleanup: How to Fix It

The short version

The cause is usually too much noise reduction or too high a gate.
Go back to the original and clean again with a lower setting.
Keep a little of the room sound; a natural room is better than a dead one.
Compare the result with the original, not only with your memory of it.

What causes it

Noise reduction works by lowering sound it thinks is noise. If it lowers too much, or the same frequencies in the voice are also lowered, the voice loses its natural texture. The result sounds metallic or underwater. A gate set too high does the same by cutting the ends of words.

How to fix it

Go back to the original recording, not the cleaned copy.
Lower the reduction and the gate. Use less than you did.
Listen to a whole sentence, not one word.
Keep the room sound a little; a dead room sounds unnatural.

What a good result sounds like

The background is quieter, and the voice still sounds like the person. A little room sound is normal. The watery sound guide explains the causes in more detail.