People's voices don't always provide clues about them. I was born and raised in the South and many people have told me that I don't "sound like I am from the South."
If you really want your mind blown, race is a man made concept utilized for organizational purposes. Genetic differences are minute between any of the races.
One bit of evidence is that sickle cell...is not a disease that affects only "black" folks. It is actually the result of having a family tree which at one time was exposed to an area of the world with exposure to malaria.