The noise is always a constant speed, but sometimes it seems to get louder. It even happens when I'm at a complete stop, with only the accessories on, and not the engine. Maybe I've just slowly gotten use to it as the brakes have worn, but I don't think I have to push the brake pedal down further then normal to brake. Also, I've gotten out and listened to it from the outside and it doesn't seem to be comming from around the calipers, it's more like right behind the plastic siding right under the window.