Modelling the acoustic signature and noise propagation of high speed railway vehicle

The proportion of high speed railway vehicles in the rolling stock of national carriers providing public transport services is constantly increasing. Currently, Alstom vehicles run at the highest speed on railway lines in Poland. The paper attempts to identify the acoustic signature of high speed railway vehicles. There are many works and studies aimed at identifying or defining the acoustic signature of high speed railway vehicles. However, the authors of these works carried out their research in a rather narrow scope, i.e. the measurement cross-section had only 1 or 2 measure-ment points with one microphone at each point. As part of the conducted experimental research, the location of testing grounds was determined, the measurement apparatus was selected and the methodology for carrying out measurements including the assessment of noise emission on curve and straight line were specified for electric multiple units. The object of the tests were railway vehicles of Alstom company, type ETR610, series ED250, the so-called Pendolino, moving on a selected measuring route without stops at a speed of 200 km/h. Measurements were carried out on the railway line no. 4 Grodzisk Mazowiecki – Zawiercie, section Grodzisk Mazowiecki - Idzikowice at kilometre 18+600 (curve) and 21+300 (straight section). When measuring the acoustic signals with a microphone array (4x2), 8 meas-urement microphones operating in the audible range were used. The microphones were placed at a distance of 5 m, 10 m, 20 m and 40 m from the track centre, at a height of 4 m (from the rail head) and at the rail head (approx. 0.8 m from the ground surface). In addition, an acoustic camera with 112 directional microphones was used to locate the main noise sources, which was located at a distance of approximately 20 m from the track centreline. The identification of the main noise sources for high speed railway vehicles, basig on actual acoustic measurements, made it possible to isolate the dominant noise sources, as well as to find out the amplitude-frequency characteristics in the range from 20 Hz to 20 kHz, divided into one third octave bands.