If you want to get a taste of that noise, then walk across the Gallows Road bridge at Dunn Loring Station or at the Cedar Lane overpass of I66.
I showed a rambler over there a few months ago... and there was considerable noise from the "concrete brook".
-doug francis, ABR Vienna
You are right about the road noise issue in Vienna and Falls Church- and in several other areas in Northern Virginia, too, for that matter. You will have to evaluate the other factors in the neighborhood such as location, price, how much you like the house, schools, amenities and so on and figure out what matters more. And when you sell that house, the new buyer will have to do the same evaluation. In close-in areas near major roads, deciding how much noise you want to live with will always be a factor. One good thing about toll road noise- it dies down considerably at night.
The fact that you are inquiring about this is an indication of certain future concerns. Factors such as road sound, airport noise, railroad etc. most definitely will impact this properties resale value and impact your quality of life there.