About 6 months ago I careered into a crater on the freeway where roadworks were being done (the road went to bare rock and dirt for a metre or so from normal bitumen) at about 90kmph. The front end driver's side immediately began to make a low harmonic humming sound which rises and falls depending on the speed. The sound kicks in at around 60kmph. Assuming it was a busted wheel bearing and with a 2000km drive in a week I took it to a mechanic to have it fixed. He said it was NOT a wheel bearing but just 'tyre noise'. After pulling it all apart again with another mechanic he had the same opinion. Have driven the car since that date constantly and had no problem. The noise is still there though, and while the car seems to drive normally, I'd prefer to get the problem sorted. There is no vibaration coming through the steering wheel etc, and about the only visible thing I can see is that a bush needs replacing. Any ideas??