# Commission Directive (EU) 2015/996 of 19 May 2015 establishing common noise assessment methods according to Directive 2002/49/EC of the European Parliament and of the Council (Text with EEA relevance), Division 2.7.2: Outline of the document

Extent: E+W+S+N.I.

The noise contour generation process is illustrated in Figure 2.7.a. Contours are produced for various purposes and these tend to control the requirements for sources and pre-processing of input data. Contours that depict historical noise impact might be generated from actual records of aircraft operations — of movements, weights, radar-measured flight paths, etc. Contours used for future planning purposes of necessity rely more on forecasts — of traffic and flight tracks and the performance and noise characteristics of future aircraft.
Figure 2.7.a
The noise contour generation process
Whatever the source of flight data, each different aircraft movement, arrival or departure, is defined in terms of its flight path geometry and the noise emission from the aircraft as it follows that path (movements that are essentially the same in noise and flight path terms are included by simple multiplication). The noise emission depends on the characteristics of the aircraft — mainly on the power generated by its engines. The recommended methodology involves dividing the flight path into segments. Sections 2.7.3 to 2.7.6 outline the elements of the methodology and explain the principle of segmentation on which it is based; that the observed event noise level is an aggregation of contributions from all ‘noise-significant’ segments of the flight path, each of which can be calculated independently of the others. Sections 2.7.3 to 2.7.6 also outline the input data requirements for producing a set of noise contours. Detailed specifications for the operational data needed are set out in Appendix A.
How the flight path segments are calculated from pre-processed input data is described in Sections 2.7.7 to 2.7.13. This involves applications of aircraft flight performance analysis, equations for which are detailed in Appendix B. Flight paths are subject to significant variability — aircraft following any route are dispersed across a swathe due to the effects of differences in atmospheric conditions, aircraft weights and operating procedures, air traffic control constraints, etc. This is taken into account by describing each flight path statistically — as a central or ‘backbone’ path which is accompanied by a set of dispersed paths. This too is explained in Sections 2.7.7 to 2.7.13 with reference to additional information in Appendix C.
Sections 2.7.14 to 2.7.19 set out the steps to be followed in calculating the noise level of one single event — the noise generated at a point on the ground by one aircraft movement. Appendix D deals with the re-calculation of NPD-data for non-reference conditions. Appendix E explains the acoustic dipole source used in the model to define sound radiation from flight path segments of finite length.
Applications of the modelling relationships described in Chapters 3 and 4 require, apart from the relevant flight paths, appropriate noise and performance data for the aircraft in question.
Determining the event level for a single aircraft movement at a single observer point is the core calculation. It has to be repeated for all aircraft movements at each of a prescribed array of points covering the expected extent of the required noise contours. At each point the event levels are aggregated or averaged in some way to arrive at a ‘cumulative level’ or noise index value. This part of the process is described in Sections 2.7.20 and 2.7.23 to 2.7.25.
Sections 2.7.26 to 2.7.28 summarise the options and requirement for fitting noise contours to arrays of noise index values. They provide guidance on contour generation and post-processing.

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Source: https://www.legislation.gov.uk/eudr/2015/996/annex/division/ASSESSMENT/division/2/division/2.7/division/2.7.2 (the official version)
Page: https://openlegislation.uk/eu-directive-2015-996/annex/division-ASSESSMENT/division-2/division-2.7/division-2.7.2
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.