Identification of noise sources of high-speed trains with microphone array and on-board measurements

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Identification of noise sources of high-speed trains with microphone array and on-board measurements

Choi, Sunghoon / Noh, Hee-Min / Kim, Seog-Won / Kim, Ki-Hwan

This paper deals with experimental works including microphone array and on-board measurements to identify characteristics of noise generated from high-speed trains. First, microphone array measurements have been performed to locate noise sources of high-speed trains (KTX and KTX-II). The array uses delay-and-sum beamforming approach and it consists of 96 microphones. In order to validate the microphone array and analysis results a measurement was carried out with two horns, generating a harmonic sound, placed at the side of a test vehicle. Results showed the array exactly locates the two horns. This paper presents noise maps for different frequency bands to identify spectral characteristics of different sources. Major noise sources are found at the head of the first car, at the trailing bogie of the last car, and the spacing between cars. The position of microphones was optimized to cover wide frequency range from 160 to 4,000Hz. Low frequency sources, found near the bogies and intercar gaps, were clearly distinguished. As for high frequency sources up to 4,000 Hz, spatial resolution was less than 0.5m and hence the radiated noise from each wheel was clearly identified. Next, the noise inside the train as well as vibration of the floor, bogie, and the axle box has been measured to investigate the cause of the interior noise. Results show two types of structural acoustic sources. One reflects the resonant characteristics of the train and has prominent peaks at certain frequencies. The other results from parametric excitation and its time-frequency characteristics resemble speed of the train. Correlation between vibration and noise has been investigated.