How Do You Record Sound in National Parks?

We've also got sounds of helicopter training in Snowdonia, low-flying aircraft in the dales. These are things that help set up a debate about sound in our national parks. And there's been quite a bit of research done in the States about sounding national parks. In some instances things have changed because of pressure that's been put on authorities with redirecting aircraft and things like that to make them restorative places.