2002 Chevrolet Cavalier Strange whirring noise while braking?

So I bought a 2002 Chevy Cavalier from a used dealership about 2 months ago. It's an automatic. After about a week of driving the car I noticed a strange whirring sound while braking. It doesn't really matter the speed I'm going but when I start to break you can hear the whirring noise and it continues until it comes to a complete stop. It doesn't sound like a grinding noise either. It's a difficult noise to explain. We thought it was the brake pads maybe but I don't have one single person who really knows what they're doing when it comes to a vehicle so we're kind of just going off very little background knowledge and what we find on google. I'm an 18 year old college student so I don't have a lot of money to go and get it looked at. Any ideas?