1.1 This European Standard specifies a direct method for characterizing the surface roughness of the rail associated with rolling noise (""""acoustic roughness""""), in the form of a one-third octave band spectrum.This standard describes a method for:a) selecting measuring positions;b) data acquisition;c) measurement data processing in order to estimate a set of one-third octave band roughness spectra;d) presentation of this estimate for comparison with limits of acoustic roughness;e) comparison with a given upper limit in terms of a one-third octave band wavelength spectrum.1.2 It is applicable to the:a) performance testing of reference track sections for