There are 3 noises you should pay extra attention to according to Angie’s List.
The first is a squeaking that persists. A little squeaking is normal, but if it is ongoing it could be a problem and cost a lot more if you wait to get it looked at.
If you hear a high pitched squealing noise that goes away with added pressure put to the breaks, it may mean you need new brake pads. Angie’s List says that just new brake pads could cost $200-$300.
Finally, if you hear a grinding noise (or some say a low growl-like noise) it can signify rotor damage. This could cause safety problems and you should get this fixed ASAP.
The longer you wait to get these things checked out and fixed, the more serious the problem could be which just means more money out of your pocket. If you hear any of these sounds or noises coming from you car brakes, get it checked out!