It appears that i have two distinct types of noise, one at ~1600 RPM, the other at ~2000 RPM. Both seems to come from the rear of the vehicle, but I cannot pin point the location. I am suspecting the rear, but I cannot feel any play in the glass (it's also a one piece glass, non-sliding).
My mechanic told me there is a hole (diameter = 0.5 inch) on the exhaust pipe a year ago. This however should not be causing the rpm dependent noise.
Any insights would be greatly appreciated!