Determination of length-related sound power levels and Input parameters for CNOSSOS-EU
Original Language Title: Ermittlung von längenbezogenen Schallleistungspegeln und Eingangsparameter für CNOSSOS-EU
Directional sound power per meter levels are the basis for most methods for calculation of train noise emissions. In Austria until now these levels were ascertained according to ÖNORM S 5026. This standard uses the sound propagation model according to ÖAL 28 to determine the sound power levels for an equivalent sound source from measured sound pressure levels. Measurements for analysis of emissions of train pass-bys were often done according to EN ISO 3095.
In contrast to ÖNORM S 5026, this standard provides a more simple measurement setup (only one standard measuring point 7.5 m away from the centre of the track is needed). As the basis for further considerations, within this project a method of calculation for the estimation of sound power levels based on measurements according to EN ISO 3095 will be developed. For that purpose, measurements of sound emission lasting several weeks will be performed. These measurements (according to both standards) will be realized with an automatic monitoring system at two cross sections with different pass-by speeds in regular operation. A comparison of the measurement results with simulations based on different propagation models (ÖAL 28, ISO 9613-2 and CNOSSOS-EU) will provide conversions possibilities together with their uncertainties.
From 2022 Austria has to use the computational model CNOSSOS-EU for strategic noise mapping. This model is also based on sound power per meter levels, but it defines different equivalent source levels for different physical sources (e.g. for rolling noise and for traction noise). Thus, a comparison or a transformation of sound power levels from ONR 305011 is not possible. Hence European commission and expert commissions have defined input parameter for CNOSSOS-EU. Direct experimental verifications of these parameters for the Austrian railway network and its vehicle types are missing. Thus, this project aims on that verification for vehicle types frequently used in Austria. Furthermore, in case of significant deviations, the parameters will be estimated. At first properties of vehicles will be systematically investigated which may have noticeable influence on sound emissions during regular operation and may have effects on input parameters of CNOSSOS EU. Following this, an iterative approximation procedure will be developed which uses sound pressure levels measured 7.5 m away from the centre of the track for verification.
By the means of logic and reasonable variation of noise components (wheel, rail, bodywork, traction and aerodynamic) derived from collected vehicles properties, levels will be searched which are confirmed by the measurement results. To make these findings available for potential users (e.g. infrastructure managers, vehicle manufacturer, freelance civil engineers, technical consulting, and experts) a guide for determination of input parameters for the computational model CNOSSOS-EU will be prepared.