Kind of hard to diagnose over a computer. Start by having the brakes and suspension systems inspected. Some observations that might provide useful clues include does the noise stop when you apply light brake pedal pressure? Does the noise only occur when braking? Do you also hear it at higher speeds?
You might be hearing the anti-lock brake system kicking in if you have that option. That should not operate at speeds below a certain speed, typically below around 10 mph.
Even the engine's serpentine drive belt and the idler pulleys can make a tinkling sound that can't be heard when driving.