2003 Saturn Ion Car making noise. Cannnot Figure it out.

My car is making a loud noise after I hit 40 km per hour. It stays loud as I am driving and then when I slow down it stops. I took it in to a mechanic and they said my hub assembly (drivers side) is shot, and I need new bushings (I think thats the name, and a new control arm which I just had changed last year. My husband changed my hub assembly at home and the car still makes the loud noise. He really didn't think that was problem to begin with anyway. It's not the exaust. We don't really know what the problem is. So even if I got those 3 things fixed by the mechanic, my car would then still make these noises. My husband took a mechanics course and worked as a mechanic for a year or so. He can fix alot of things on his own, but he is stumped as to what the noise could be. Any ideas would be appreciated.