Acoustical Source Modelling for Rolling Stock 9HKLFOHV WKH 0RGHOOHU¶V 3RLQW RI 9LHZ Andrea Bistagnino ALSTOM Transport, Saint-Ouen, France. Giacomo Squicciarini Institute of Sound and Vibration Research, University of Southampton, Southampton, UK. Ulf Orrenius Bombardier Transportation, Västerås, Sweden. Estelle Bongini SNCF, Paris, France. Juan Sapena ALSTOM Transport, Saint-Ouen, France. David Thompson Institute of Sound and Vibration Research, University of Southampton, Southampton, UK. Summary In the framework of the European project Acoutrain, a deep study of the validity of current, state- of-the-art predictions of the exterior noise of rolling stock vehicles has been performed. Although different international standards exist to measure the sound power level of noise sources, this quantity alone is insufficient to create reliable source models, as directivity information is also required. The same measuring techniques used in these standards can be adapted to obtain the data needed for accurate source modelling. In this paper we address the issue of source modelling for the case of rolling stock vehicles; we present the mostly widely used techniques used in this sense and compare their results with measurements both at source level and at train level, showing the impact this has on full train noise prediction. Lastly, we discuss the relation between source modelling in general and the experimental characterization of the sources, including an analysis of the consequences this has on current practices in this domain and on standardization of testing techniques. PACS no. 43.50.Lj 1. Introduction The main objective of the European project Acoutrain [1] was the development of methodologies to introduce elements of virtual validation in the certification of trains according to TSI NOISE. This should be based on calculations capable of predicting noise levels with accuracy at least comparable to that of the measurements on the train. Clearly, one of the most important challenges to reach this objective is the availability of reliable models of the trai Q¶V QRLVH VRXUFHV ,Q particular, one of the objectives of Acoutrain was the minimization of the measurements required at train level: we would like then to be able to characterize single sources in free-field and then place them YLUWXDOO\¶ on the train and calculate the global level of the train. This study presents the analyses done for the HVAC unit of an EMU train used for part of the validation activities done in Acoutrain; the unit was characterized alone in free- field in a first test campaign, and then measured when installed on the train. Two calculation tools have been used within Acoutrain and in this study: SITARE and ACOUTRAIN-tool. The first one, SITARE, has been developed exclusively for ALSTOM and since many years it is the reference tool for exterior noise calculations of ALSTOM [2]. ACOUTRAIN-tool has been developed by ISVR specifically for the Acoutrain project. The two tools share the main approach to the calculation of noise levels: Copyright© (2015) by EAA-NAG-ABAV, ISSN 2226-5147 All rights reserved 1991