I drive on all different surface; motorway, smooth, rough, bumpy. Sound stays the same, as well as turning left or right I can't tell any difference in noise change. Most forums I've read about say its the bearings as they say recent bearings don't show play or noise when you spin each wheel. It's very annoying and I know what you mean if I go change bearings and noise stays the same I will be really annoyed.
Thanks