'04 Jeep Liberty: "Squealing" Noise

Last night when I started driving, I heard a rattling noise. Then, my entire way home, the sound sounded like bats when they're rustling around, or maybe like a CD player when the player changes discs. Kind of like a "squealing" noise. The noise amplified when I would break, but it was silent when I was completely stopped. I took it to the quarter-carwash this morning to wash the under-body to see if it was just dirty, but it didn't help. I asked some friends today and they said it sounded maybe like a pulley or belt problem, but not sure. My mom took it for a ride this morning and said it might have been coming from one corner of the car, as if a wheel area. I just got new break pads last year and new breaks this year.