If you're bothered by aircraft noise in the area, then this is for you. Roughly half of planes arriving and departing from Heathrow belong to the Airbus A320 family which have been in service for a number of years. You always know when one of these is around because it makes a high pitched whistling noise, unlike the lower rumble of other planes. This whistling is generated by air flowing over a number of holes in the wing called Fuel Over Protector Cavities. Only now has a fix been manufactured, which is being implemented by a number of airlines. Lufthansa and Air France have almost finished with their Airbus fleet. BA (i.e. the prime noise generator at Heathrow have yet to start, but allegedly will do so in October 2015). If you're wondering, the noise difference is immense. A Lufthansa A320 is not audible indoors, and not intrusive outside. More information here: http://www.greenaironline.com/news.php?viewStory=2116