This paper gives an overview of the results and conclusions from measurements made with various configurations of microphone arrays designed to locate sound sources on trains operated by the Deutsche Bahn AG at speeds up to 280 km/h. These arrays comprised one- and two-dimensional arrangements of up to 29 microphones. The characteristics peculiar to microphone arrays will be mentioned only briefly here, because the theoretical background of array measurements is available in other publications. Within the context of the present paper, the sound sources located are those generated mechanically, principally by wheel/rail interactions, and those produced by aerodynamic fluctuations. In addition, noise radiation from cooling systems was also measured during passages of the trains. Examples are given of results obtained with different kinds of arrays during pass-bys of dedicated ICEs and goods trains. These examples demonstrate the usefulness of array measurements for producing detailed information pertaining to the characteristics of individual sound sources. With respect to these individual sound sources, particularly on moving vehicles, array technology provides a much more efficient and capable tool for investigating these sources than does the more conventional technique employing single microphones. (C) 1996 Academic Press Limited
