NOISE IMPACT OF AIRPORT DEVELOPMENTS

In the early days after world liar ll, Heathrow Airport was developed as London's major International Airport and its increase in size to a three terminal airport in the 1960's was not significantly impeded by planning restrictions.The introduction of jet aircraft in 1953 had caused a marked rise in the number of'noise complaints and the Wilson Committee [I] in 1963 considered the noise problem at Heathrow as 'acute". THE NOISE AND NUMBER INDEX (NNI)The Uilson Committee instituted the social survey which lead to the production of NNI, relating measured noise level and number of aircraft to annoycnce.Their investigations were concerned with ways of dealing with en existing noise problem and concentrated on reducing noise levels of aircraft and improving the sound insulation of houses around the airport by a grant scheme for double glazing.The planning of future airport developments was not considered; the position of Heathrow as the major London airport uas alieady established and the Wilson Committee could not believe that Heathrow could cease to be a major airport.NNl was subsequently used in all Airport Inquiries for the next 20 years for evaluating aircraft noise.The relationship was N'NI = 15 log N +-Average peak noise level -BO.Hhere N is the number of aircraft above 80 PM]! between 0600 and l800 GMT on an average day between June and September.The average noise level is in Perceived Noise decibels (PNdB).The Wilson Committee found that between 50 and 60 NNI aircraft noise becomes 'intolerable".Subsequently the following degrees of 'annoyance" have been used at most Public Inquiries: 35 NNIlow annoyance 65 NNImoderate annoyance 55 NNIhigh annoyance 3.GROUND NOISE Noise from aircraft on the ground was briefly considered by the Wilson Comitteethey appreciated that running of engines on the ground caused