Could be a wheel bearing or a CV joint. Usually bearings are a constant whir or grind, whereas a CV joint is more of a tick or click, and it can sometimes be worse when you are turning left or right.....but to be fair, they may all sound a little bit different, so you'll want to make sure you diagnose it properly.
You might jack up the wheel you suspect and check the CV joint and/or spin the wheel and listen for noise, check for looseness, etc..
Good luck! Glen