Tire rubbing sound

I Have a 05 impala, i bought it with 18'' chrome rims, but recently it started making a loud rubbing sound at about 15 mph and over, its really annoying, rim shops have told me its just road noise, but its too loud to be road noise.

Is the noise coming from one corner or all over? Was it doing it since you bought the car, or is this a new noise? If only one corner, rotate the tires and see if it moves with the tire/rim. If all over, what brand tires do you have? How's the alignment? Many times oversized tires with a different offset rim will cause alignment problems.

I am guessing here that this rubbing sound is a constant and not intermitant. It is quite possible you have a wheel bearing unit failing, determining which can be difficult, does the sound increase or decrease when turning left or right? It is also possible the brake caliper(s) are not releasing fully and the slide pins need replaced or properly cleaned and lubed. Are these after-market wheels with the proper offset? Not a complete list of possibles but a starting point....