Ianr, thanks for the reply. I assume it's Heathrow bound traffic as they're mostly very large planes (747s etc) when observing from the street. The statistics would definitely be interesting. There's certainly many variables with regards to aircraft audibility, but it's been nearly 1 week now of frequent low flying noise that I'd never noticed to this extent before. Just some Heathrow provided information (more so than tracking an aircraft that was overhead 1 hr prior) would be helpful at providing some insight and understanding!