I am experiencing a sound at low speeds (almost at a stop) where it sounds like the brake pad is grabbing the rotar and then releasing.. almost a vibration sound but with a lower frequency. I also have a vibration in the front when braking hard at speeds over 70. Off the top of my head this seems to be a warped rotar. I only have 3600 miles on the car so I'm wondering if they just need to 'break in' a bit. It did not do this from 0-3500 mile mark because I would have noticed.