If it's coming from the wheel, and only as you turn, it may be your CV joint. Usually what happens is that the rubber boot rips and the grease leaks out. When there is no more grease then the gears start to grind.
You want to get it looked at right away before it does more damage. It's possible that you could just have a new boot installed and the joint will be fine. If you leave it, the joint could eventually break and you could lose control of your vehicle at that wheel.
〉 Answered on Dec 16th, 2008 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines