My GS300 brakes had a really annoying, loud rattling sound as well as the droning/humming noise. I knew the bearing on the right was shot, but focusing on the rattling I changed everything - sway bar bushings, droplinks, brake pads etc & the noise continued. My nephew convinced me that both bearings were very bad as he could reproduce the noise with the wheels off the ground by basically thumping the tyre to recreate it hitting a bump. I had them changed (bought bearings for £100 from auto factors, and fitted both sides for £120) and the rattling is gone now.
There is a barely-perceptible 'clunk' remaining when you put the car in gear or reverse or put in a full lock, but I'm going to install a brake fitting kit & hope that really sorts me out.