There's no traffic passing through the campsite itself, the marshals do a very good job on the gates with passouts, there's some noise noticeable from the motorway early in the week when the site and track are quiet, obviously it's noisy from the track during the race & practise but that's what you get for camping trackside.
I was shocked when I first visited other campsites & saw that anyone who wanted could wander in and out.