Heathrow Airport - Noise impact?

I recently found this page, while searching for potential impact of leaving too close from the world’s 4th busiest airport (LHR). I live in Putney: although we certainly see a bunch of planes flying in our sky, I would think the noise pollution is fairly limited here.
Anyway, I found that LHR were extremely proactive here, by listing areas potentially affected by noise, also gathering information with regards to development plans in the pipeline. Now, imagine for a second, you purchase a property around London, and two years later, BAA develop a new terminal at the end of your garden….. I know that sounds funny, but I would bet many people have found themselves in that awkward position already
Anyway check here for more info on LHR!
Hakan.org also displaying very useful information on that subject
