I am sure I have seen a thread on this some place, but I am having difficulty tracking it.
When I have the roof down and I go over any uneven surface there is quite a knocking noise form just over my right shoulder, so for UK set up cars its on the driver side. You can hear it every now and then on the ofther side too but the road really has to be very poor to hear it on that side.
The noise seems to be somthing to do with the roof mechanism, I am sure I have seen a thread on this re dampers or somthing like that
I've noticed that with the top down, IF the seatbelt is NOT running through the "loop" at the top of the seat, it vibrates as the speed increases. Semi annoying to the point where I always try to keep the "loop" clipped closed around the seatbelt.