Directivity of railway noise sources

In the Harmonoise project the description of vertical and horizontal directivities of railway noise sources has been required. Other features of the source description are sound power level spectra in one-third octave bands as a function of speed and the physical location of the different sound sources.Based on systematic investigations methods to measure and to determine the directivities of railway noise sources are presented in this paper. The determination of the directivity of rolling noise is discussed in detail. For the directivities of traction noise and aerodynamic noise the discussion is more analytical because of limited access to relevant data.For each type of main railway noise source, i.e. rolling noise, traction noise and aerodynamic noise, default directivity functions are proposed for the use in the source description of railway noise. These default directivity functions will be subject to revisions when more accurate data become available.