If the sound occurs during the spinning cycle only it might be a sign of worn bearings, move the drum by hand when emty and listen carefully for the sound the bearings make, also try push the drum upwards if more than a few millimeters of movement it is definitely the bearings, otherwise it might be something trapped like a wire (bra underwire) or object that could make it's way through the holes in the drum.
Grant
November 2005