Well, I have just conducted a very un-scientific study on the cabin noise levels in the Passat. I downloaded a cool free decibel reader app on my Ipad. I compared the decibel readings from my Passat and my Civic at 40, 50, 60, and 70 mph and here are the results.
MPH Passat Civic
40 68db 72db
50 70db 78db
60 71db 74db
70 73db 78db
peak db 86 95
My only explaniation of why the civic went down at 60mph is that at 50mph there seemed to be a lot of road noise, then at 60 it quieted down and then the wind noise took over at 70.
Both cars were taken on the same route with the same speeds in the same part of the road.
The peak decibel reading were on a rough surface of the road.
The Passat has the continental tires.
Conclusion, The Passat with the continental tires is very quiet and as the speed increases the elevated noise levels come from wind noise and still remains relatively quiet. The Honda is a soup can on wheels. lol