thevelvetglove

there seems to be a strange noise that sounds like scraping on the break rotor rear left...can't quite tell

1) It only happens now and again
2) Very short periods of time 3-5 seconds
3) Does not happen when I break
4) Seems much slower than the turning of the wheel
5) Sounds like a rusty scrape on an old peice of metal
6) Seem to be more prevelant when accelarating from slow speeds.
7) Is intermitant for very short peiods of time when accelerating from slow speeds

What in the hell is this?