Harmonoise: simplification of comprehensive source andpropagation models into an accurate and practicableengineering method

摘要

The Harmonoise engineering method is developed for computation of long-term noise indicators Lden and Lnight. Since sound propagation effects can strongly depend on meteorologicalconditions, the method must be able to handle different meteorological conditions that occur during ayear. In order to obtain a more accurate description of the sources, a subdivision into subsources atdifferent heights is necessary, distinguishing different physical mechanisms: rolling noise, tractionnoise and, for high speed trains, aerodynamic noise. Combining such comprehensive source andpropagation models into an integrated method for use in complex 3-dimensional noise maps, a balancehad to be found between the accuracy of computation versus computation speed, requiringoptimization and simplification of algorithms. On the other hand, for continuity of the model,additional algorithms had to be developed to improve methods that have been developed merely for‘academic cases’. The Fresnel-zone weighting principle, adopted from the Nord2000 method, caneven be extended to reflecting and diffracting obstacles with finite length. Algorithms have beendeveloped for transformation of meteorological data into an equivalent ray curvature, depending onthe direction of propagation and local geometry. The resulting engineering method is flexible in such away that it can be used both for detailed computations in case of noise assessment and for noisemapping, requiring a higher speed of computations. This computation time is saved by reduction ofinput data, using the same calculation engine.