97 Suspension Question

When backing out of the driveway (slow speed) hen the driveway meets the street I hear a knock coming from the rear of the vehicle. This is annoying so I performed a test.

I stood on the back bumper and jumped up and down (220lbs) Car gently raised and lowered and didnt make a peep. Its never had any suspension work done so I wouldnt take this as "my suspension is fine". However if I go to a wheel and rock the vehicle from the location of the wheel I can hear what I think sounds like what Im hearing when I back up.

I tried to put my ear down there but i couldnt do both (duh). it kinda sounded like it was coming from the leaf springs but I heard it on the front too. Any ideas.