Quantitative Evaluation Method of High-speed Railway Noise Depending on Noise Generation Mechanisms

Abstract

In this study, quantitative evaluation methods of high-speed railway noise depending on noise generation mechanisms were suggested. Stationary noise of high-speed train interior was measured. To examine the perceived annoyance and the perceived sound volume of interior noise of high-speed trains, two auditory experiments were conducted. It was identified that loudness was better for evaluation of the perceived sound volume than A-weighted sound pressure level when various noises with different sound pressure levels and loudnesses were compared. Also a combination of loudness and sharpness which reflects the aerodynamic noise effect of high-speed train was better for evaluation of the perceived annoyance than A-weighted sound pressure level. Transient noise in passenger compartments was measured for short durations in order to understand the effects of various operating conditions such as running through a tunnel, and passing another train. A new method to quantify the annoyance was proposed based on sound quality metrics and derivatives of their time-varying values. It was verified that the proposed index, the maximum gradient value of sharpness, had a very high correlation with the annoyance under a sudden noise change, when using level-equalized sounds. To reflect binaural characteristics of train pass-by noise, binaural measurements were conducted for several train types, different measurement distances and various measurement angles. The annoyances were compared between measured monaural and binaural noises for the same pass-by noise. Similarly, for the same binaural pass-by noise, the annoyances were compared for different measurement distances and angles. It was identified that there was a binaural effect on the annoyance. To reflect the binaural effect on the annoyance, the maximum change rates of difference between left and right channels of loudness and sharpness were proposed to evaluate the annoyance of pass-by noises. The high-speed railway pass-by noise was characterized using time-frequency analysis. With the time-frequency analysis, it was examined that inter-coach spacing noise had a great contribution to the noise. Considering the inter-coach spacing noise contribution to the pass-by noise, the Doppler effect on annoyance was determined through an auditory experiment using synthesized moving sound sources with a different Doppler shift. To reflect human hearing perception, a head-related transfer function was also applied to the synthesized moving sound sources. By conducting an auditory experiment, it was determined that the Doppler effect made perceived annoyance decrease.