Subaru Forester 2014: What's causing a knocking sound?

When I go around roundabouts I get a knocking noise under my 2014 Subaru Forester. It is either at the back or in the centre of the car. It's hard to tell. And when I reverse to the right there is a scratchy sounding noise. My old neighbour reckons it is either brushes or boots? I don't know what those things are. Should I go to a suspension business? The car is out warranty by about 12 months.