knocking sound & humming sound

I could answer a little more completely if I knew the type of vehicle. Nonetheless, the knocking noise could very well be a failing CV joint in the drive axle. A humming noise as you described sounds like a possible wheel bearing. A wheel bearing noise will make noise more severely when turning, and more so on the opposite side of the direction of the turn. Both are important to repair, but likely will not cause an immediate failure.