A New Type of Line-Array for Acoustic Source Localization at Drive-By Tests of Trains

The microphone array method together with the beamforming technique, required for the post-processing of the recorded acoustic data, has been optimized for measurements on moving rail vehicles. In order to increase the spatial resolution along the moving vehicle a new type of microphone array was developed. This comprises a line array in combination with a two-dimensional elliptical acoustic mirror. Acoustic source were separated successfully using the properties of the elliptic mirror along the trajectory of the train by applying the beamforming methods for the vertical axis. The combination of both techniques allows a three-dimensional reconstruction of the source distribution. The design was successfully tested on a high speed train track in Germany, which is used by different type of Inter City Express and other passenger trains. It was possible to improve the quality of the results significantly and individual wheel sets and aeroacoustic noise caused by roof structures can be identified in the source maps. The resulting acoustic source data obtained with the microphone array technique, provides input data for noise prediction methods, which can fill gaps in existing noise source databases thus assisting in the goal for a deeper understanding of rail vehicle noise.