My daughter doesnt hear it. I think its KIA SOUL loud. Sounds there are no sound deadening in the back. We are a GM family. One of our trucks is lifted with 37’s and is quieter than my daughters car. Wifes Caddy is smooth and quiet. Sound like a rear end metallic, almost warped rotor noise or whirring or woop woop woop woop, not a steady whir.
I Kia Soul is not a Cadillac so that’s an apples vs. oranges comparison. Arrange to have a good mechanic drive it and see if he agrees about the possible brake noise.
Then why do you think it is a problem? If it worries you, have a mechanic look at it. It might just be a noisy car.
I test drove a KIA SOUL and it was not what I would call loud.
Doubtful it’s a rotor noise (tire or wheel bearing maybe???) but my daughter in law has had a Kia Soul for 4 years and does not have this issue.