1998 Acura RL

Hi I been having a problem with my car for almost two weeks now when I start my car is fine, but when I am ready to press on the gas for about 10 to 20 mph my rear tires make like a weird noise like it scraping the tire little by little and then it stops I just got my tires changed two days ago they were a little uneven and when I am about to press on the gas again it does it again the scraping noise can you tell me what going on and do I need a aligment and what does that do for my wheel and tires because it would be my first time experience. Thank you