I remember standing by Silbury and being amazed by a massive low rumbling, which turned out to be people drumming inside WKLB. Stonehenge would be far less effective presumably because of the shape.

I liked this: "an app which will help people blot out the sounds - including those made by tourists, and cars on the nearby A303 - and go back to the soundscape of 3,000 years ago." What's the betting EH will buy it and suppress it? The road noise is their main excuse for supporting the short tunnel project.