I have a 2009 Hyundai Tucson when I back up my SUV makes a noise,the brakes were not applied. Has anyone heard of this problem?

my son has the same problem a high whirring noise.. he is getting his rear rotors and pads changed this week.. which should resolve the issue. his rear rotor noise began after having a garage replace his rotors last year and they put the old pads back on the new rotors the new ones were sitting in the back seat with the new rotors.this damaged the new rotors and messed up the ebrake cables. ebrake cable was dragging on the brake system replaced the cables and developed the noise now the new pads we put on after the new rotors were damaged are shot as well. i suspect warped rotor due to heating and cooling and dragging on system now the pads are worn down we are replacing all i would replace rotors pads and have the e brake cables replaced if there is play in your ebrake handle and it does not engage within the first 3 clicks pulling up on it. the noise i suspect is the rotors are warped.. but to resolve the problem and prevent from reoccurring you need to figure out why they are warped..