I downloaded your latest file. pressed to bake and this is what I was given. the problem remains. Of course if you put a bunch of flat and put it subdivisions blender can bake normal and subdivisoins give smoothing. But this is not the solution

I have attached the file. In the file you just have to press and bake in the UV will be the normal map. On the normal map visible noise. I used to render Cycles. When I change the direction of the normals of objects Hight poly and Low poly and bake it the problem disappears and the noise does not appear.

Sorry! Version 2.72