ABSTRACT
Historical noise assessment methods and their range of applicability .... 312 Parts of a noise assessment method ....................................................... 313
Source ............................................................................................... 313 Propagation ...................................................................................... 315
Noise assessment methods used in Europe ............................................ 315 Major methods ................................................................................. 315 Minor methods ................................................................................. 316
Elements of the existing noise methods leading to differences in the noise assessment .................................................................................... 316
Set of input values ............................................................................. 318 Formulas used for the description of the source and propagation ..... 319
Analyses of the differences in noise assessment ...................................... 320 Available quantiable parameters ..................................................... 320
Leq ................................................................................................ 320 Spectra.......................................................................................... 320 Population exposure ..................................................................... 320 Source sound power denition...................................................... 321
Uncertainties in the determination of differences among noise assessment methods .......................................................................... 321
Interpretation of the standard ....................................................... 321 Software implementation .............................................................. 322 Different denition of the input parameters .................................. 324 Software settings........................................................................... 326
Objectives of existing noise assessment methods according to the Environmental Noise Directive (2002/49/EC) ................................... 326 Overall evaluation of the differences in noise assessment .................. 327
Past comparison studies among existing noise assessment methods ....... 331
HISTORICAL NOISE ASSESSMENT METHODS AND THEIR RANGE OF APPLICABILITY
In environmental noise assessment, noise mapping methods are used to assess the levels of noise over a large amount of positions forming a grid of elements, eventually equidistant one from each other. The rst noise calculation methods in Europe were developed in the 1980s, and most likely at that time the objectives of the assessments were focussing on the most exposed locations in an as far as possible advanced manner. Although calculations were considered to be made eventually via the use of computers, evidently the way the rst methods were written was triggered by the need to allow hand calculation of noise at single locations. Calculations at those times could already benet from the rst extensive measurements aimed at characterising the noise sources, typically near the source itself, which were then used as test cases to verify the correctness of the calculations themselves. Until recently, the testing against source data and simple cross-sections and only next to the source has remained as the most used strategy to prove the validity of the existing noise assessment methods in such limited conditions. For several methods, some combinations of source parameters and propagation parameters, which are difcult to effectively handle by means of physical descriptions, were modelled by the use of correction factors. This is, for example, the case of the correction applied to the noise produced by trains on the basis of the commercial denition of the type of track, which is nowadays instead implemented as a specic model depending on physical parameters such as roughness, pad, stiffness, and sleeper type. The same applies to meteorological corrections that were making use of an average correcting factor, whereas nowadays modelling of the meteorological effects is based on physical parameters like wind speed and temperature gradients.
