Adamtc1

I just bought an 04 rx8 and its making a really loud noise almost sounds like a reving sound but coming from the rear end and only occurs if the car is in motion, so if I am in neutral and rev the engine it does not occur. With some automotive repair knowledge we are pretty sure that it is the drivers side rear wheel bearing. I am going to order the wheel bearing but was wondering if it has to be compressed? Can anyone help or experienced this themselves?