My wife has a 1.6.16V Megane cabriolet. Its 9 years old and she loves it. Its an automatic with approximately 75000 on the clock. When driving a noise that I can only liken to a humming vibration starts once you hit around 40mph and it continues to get louder the faster you go and it quietens down when you slow down. It seems to be coming from underneath towards the back of the car. I think it may be the exhaust but as my prior technical experience of vehicles was as a B1 driver in the AAC I am somewhat limited in my erstwhile knowledge. Thus I would be indebted if any knowledgeable greasemonkeys or persons of a similar ilk could possible throw some light on this. Muchos Grassyarse.