My Tuscon started with a noise at the rear wheels....or at least it sounds from the rear wheels. It is a humming noise which becomes louder from 20km/h. It is better at high speed but is never gone. I have already done wheel alignment and replaced the rear tyres with new tyres. The noise never subsides. Can anyone please advise what can cause this. I can only think it is the wheel bearings???? The car has done 87000 km.