As someone who has in the past lived 250m from the BHD perimeter fence in East Belfast I can tell you that the only noticeable noise comes from jet departures and the Let410s. The road noise from the Sydenham bypass generates more noise than the majority of the departures and arrivals. The flybe Dashes are very quiet - all you hear on departure is about 2 seconds of a "burrrr" noise, no louder than a van driving by outside of the house. Jet departures and reverse thrust by jets on arrival make louder and more persistant noise.