Very peculiar sound...

I have a 1997 Nissan 200sx SE. When I am just coming to a gradual stop, maybe last 10 yards before a stop light travelling approx 40mph, there is a clacking noise "clack clack clack, clack, clack; clack; clack". I have checked out my brakes and they are quite full, front and back. But here's the big mystery: when I use my E-brake to come to a complete stop... THERE IS NO CLACK. Note: My brake pads are full, I am pretty sure I do not have ABS; I read something about a 'anti-rattle' bracket? Also, the brake petal does not vibrate, there is no apparent effect on braking or operation from the noise, any help would be great
Thnx