Additive evaluation criteria for aircraft noise
The occurrence of unexpected aircraft noise events will frequently evoke intense complaints about annoyance over such events. It is recognized that the relationship between the volume of complaints and the corresponding maximum noise levels does in fact depend on the circumstances of the complainants and the time of year. The frequency of occurrence of the respective noise events is also a factor. The possible practical value of the addition of the maximal noise level, to the well-known cumulative noise descriptors L(sub eq), L(sub dn), etc. may be considered. One might start by considering the difference between the L(sub eq) and the average maximal noise level of the twenty loudest single noise events on an average day. A somewhat less sharply focused consideration of the maximum noise levels was adopted. In that standard the scope of noise-mitigation measures is defined generally with reference to L(sub eq). If the average maximal noise level L(sub max) of the entire aircraft fleet mix exceeds the L(sub eq) by more than 20 dB(A) and if more than 20 daily aircraft noise events exceed the L(sub eq) than the difference L(sub max)-20 becomes the key criterion for noise-mitigation measures. A statistical correlation of a large number of data from aircraft-noise-monitoring sensors located both directly underneath and laterally disposed to an aircraft flight-path has supplied a basis for the determination of the distribution of the maximal noise levels about the average value, L(sub max), of each type of aircraft. This distribution is given for the takeoff climb and for the landing approach.