from my experience there is one easy to determine the difference between tyre noise and bearing noise, tyre noise is more evident at lower speeds and wheel bearing as higher speeds. tyres hum and bearings growl, sometimes also have a squeek. If you feel the tread of your tyres, its should feel smooth, If it feels uneven (up and down like waves)usually on the inner edges, this can cause noise, some times the tread pattern ,especially directional tyres can cause noise, even when the tyre is new. Good brand, bad brands it doesnt matter sometimes. On one car I have had Bridgestone G Grids, they were noisy, on my other I have cheap chinese tyres, they are noisy too. Make sure you tyre pressures are right too. can make a difference. Hope you sort out your problem :D