It could be a number of things but mine was noisy from day one and steadily got worse until I was convinced that a motor bearing was collapsing. On stripping it down I found that the RH side blower which is made of plastic had a loose impeller. The impeller sits on the splined shaft of the motor and is only held there by a spring clip (just like a hose clip over the slots in the impellor) it had become loose, it sliped on the motor shaft on start up and at every change of direction producing a grinding scream and a lot of vibration. I removed the impellor cut a few shallow splines in the plastic. Packed the shaft by winding it with PTFE tape and re-assembled - Result quieter than it had ever been and seems to dry quicker.
To access the guts first disconnect the power, remove the top by taking out the two screws at the back edge. Use a rubber mallet or strike the top front edge with your palms to get the top to slide back and lift off. (note you realy have to hit it hard I thought it was going to break but by then I didnt care!). Undo the 4 off screws on the back edge of the Right Hand panel and the one at the top front edge of the panel. Slide the panel backwards and off.
You should now see the motor and the grey plastic box that forms the blower. Cut the retaining cable tie and swing the cables free from the box. With a flat blade screw driver or similar pop the clips and lift off the top of the blower box. Remove the impeller neck ring (plastic disk with a hole in it) then you can get pliers inside the impeller and remove the spring clip. Renew Impellor or fix it then re-assemble in reverse order NB turn the drum and hence the motor to make sure the impeller is not catching before boxing up. the impellor should sit well on the motor shaft with a moderate gap between the impellor and neck ring - too little and it may rub, too much and the blower efficiency falls as air is sucked back around the impeller
Phil Slack, March 2010