weird

Hello!! Bought a 2014 Tahoe LS 4WD and runs perfectly fine just what are those clunking sounds underneath at rear sounds like (marble hitting aluminum can, etc.) 10sec intervals right after I shut off the engine? Could it be metal cooling down or is this normal?

Ok, when I am traveling at or above around 40 mph, a weird noise that sounds exactly like a cd player skipping or searching comes from the rear/cargo area of the car. It seems to be made worse when i go over a slight hump in the road, but as soon brakes are applied it goes away. Can anybody...