Audit Select Committee, published in July 2006, which labels the government strategy a predict and provide model and expresses scepticism about the timescale and efficiency of the EU ETS. It recommends instead that the government rethinks its airport expansion policy and considers ways, particularly via increased taxation, in which future demand can be managed in line with industry performance in achieving fuel efficiencies, so that emissions are not allowed to increase in absolute terms. Local environmental effects Under the provisions of the Civil Aviation Act aircraft in flight are specifically exempted from trespass and nuisance controls, which denies any form of redress to those living near airports who are disturbed by noise. Government sanctioned measurements of noise near airports take an average sound level, measured in decibels (dB), over a 16‑hour day, and are expressed as an LAeq figure. Officially, 57 dB LAeq is the threshold at which noise levels become disturbing, 63 dB LAeq represents moderate disturbance, whilst 69 dB LAeq represents high disturbance. Technological improvements in aircraft design means that aircraft are becoming quieter. Taking Heathrow as an example, between 1990 and 2004 the area around the airport affected by noise levels of 57 db LAeq and above fell by 60 per cent, whilst the number of people similarly affected fell by 51 per cent. Campaign groups dispute the methodology used to measure noise, asserting that it is flawed in a number of ways. Amongst other issues they point to the World Health Organisation view that annoyance begins at 50 db LAeq whilst serious annoyance begins at 55 dB LAeq, and they assert that the LAeq measurement does not give sufficient weight to the increasing incidence of noise events. Their conclusion is that noise levels, and the number of people affected, have increased rather than decreased. This is borne out by the latest survey of attitudes to noise published in November 2007 which reports that, compared with over 20 years ago, more people today are annoyed by the same level of noise as measured by LAeq. Whilst this may be attributable to changing attitudes, the report concludes that the contribution of aircraft numbers to annoyance has increased, and that an alternative method of estimating levels of annoyance that takes this into account would appear to be more relevant than the LAeq measurement. The report has attracted criticism in peer reviews, and one such review, characterising the survey as