Assessment methodology for pressure-related aural discomfort in high-speed trains using airtightness experiments and mathematical models

This study aimed at establishing an evaluation methodology for aural discomfort induced by the interior pressure changes in high-speed trains running in tunnels. Experiments in pressure cabin, which can reveal the relationship between aural discomfort and pressure change, were discussed. Furthermore, a human middle ear model was used to simulate the vibration. The experimental conditions were considered as pressure loads, which were exerted on the tympanic membrane. Furthermore, the aural discomfort was hierarchically divided into four levels: ideal, good, bad, and worse. Four indicators, such as the tympanic membrane displacement and stress and the stapes footplate displacement and velocity, were used to establish the discomfort criteria. Logistic regression analysis was used to investigate the incidences of each level as well as to obtain the thresholds between levels. The outcomes have a p-value of less than 0.05; hence, the response results of the indicators are statistically significant. Additionally, the thresholds of the indicators were obtained and used to differentiate the aural discomfort levels. The intervals of the four indicators are (0,T1), (T1,Tc), (Tc,T3), and (T3,>T3) for the discomfort levels of ideal, good, bad, and worse, respectively. Moreover, the onset mechanism of aural sensations was revealed using the four indicators. It can be implied that large tympanic membrane and stapes footplate displacements tend to elicit ear complaints, such as fullness, otalgia, and vertigo, whereas the large stapes footplate velocity affects the onset of tinnitus and hearing loss.