Sound Source Separation on ICE 3 High Speed Trains Based on Combined Sound Pressure and Sound Velocity Measurements

A measurement method is presented that allows a separation of sound sources based on pass-by measurements of trains. It combines a sound pressure microphone with two sound velocity transducers, all of which are positioned at one point. The velocity transducers are employed as directional microphones. The true source positions and their sound power are determined by solving an inverse problem: In a system of propagation equations the source positions are optimized until a best fit to the measured signals is achieved. Measurement results are shown for pass-by measurements of German ICE 3 high speed trains at speeds between 200 and 250 km/h. The extended pantographs are thereby identified as dominating sound sources in the upper part of the vehicles. The measurements yield reproducible results and are in accordance with data taken from literature. The method represents an alternative to the array measurement technique although with a considerably smaller measurement and data analysis effort. Information on the sound power of multiple sources is gathered with an accuracy comparable to array measurements. The localization of the sources is though less precise and the separation is limited to two sources at a time. Therefore the measurement concept can not be seen as a general replacement of the array measurement technique. Nevertheless there is a broad range of applications where a. ne spacial resolution is not of major interest. In these cases the method is likely to represent an appropriate substitute.