The Impact of Distance and Altitude on Railway Environmental Noise Based on Cerebral Oxygenated Hemoglobin Saturation.

Railways are considered an environmentally sustainable mode of transportation but can pose significant environmental challenges due to their operation and associated activities. Among these, noise generation is a persistent source of public complaints. In Korea, a maximum distance of 100 m from buildings has been proposed for new railway developments in residential areas, although this guideline lacks a solid foundation based on experimental evidence. Noise barriers are often installed as a mitigation measure; however, there is no standardized guideline for their height in relation to their effectiveness at varying distances. The distances and altitudes set in this study took into account accessibility and the height of noise barriers on actual railway sites. In particular, we examined the effects of altitude above and distance from a railway site under the assumption that the prefrontal cortex would be physiologically affected by noise exposure. In this study, we conducted the first analysis in Korea of cerebral blood flow changes in response to noise, to assess quantitatively the stress effects caused by railway environmental noise at varying distances from, and altitudes above, a railway. Using functional near-infrared spectroscopy (fNIRS), we measured prefrontal cortex activation in 10 adult males (average age: 33.2 years). Brain activation was evaluated under different distances from (40 and 100 m) and altitudes above (1st and 4th floors of a building) a railway through a paired-sample