Dr. Stephen, I purchased my 2012 Linea in March too. I hear the same noise. After pushing the service center for a few weeks, i got them to identify the source of the issue. The spot welding in the C-Pillar is defective at a few places. In my car this is affects both left and right pillars. The service centre told me that they need to take out the rear glass and the quarter glass on the rear windows to rectify the weld. This is risky as there is a chance of the glass pane breaking. They were waiting for FIAT to respond with the operating procedure. It has been more than 4 weeks and I am still waiting. I have made several calls to the customer helpline and have raised written complaints. This is certainly a manufacturing defect and I am not sure why Fiat is sitting tight on this.