How many miles on it? Is it a clanking noise or more of a clicking noise? If it is a clicking noise when the tire is turned hard to one side it is most likely one of the CV joints. Find an empty level parking lot where you can drive in a circle in forward and reverse with window down and listen for a what I would describe as a clicking sound. It will be easy to figure out if it is the left or the right.

Another thing to look at if the mechanic did not already is inspect the rubber boots covering the CV joints. They may appear very clean and in tact but if one has a slit in it, it may have already lost grease and introduced water and dirt into the joint thus causing premature wear.

Good luck!